Menstrual cycle

The menstrual cycle,

is a series of physiological changes that can occur in fertile females. Overt menstruation (where there is blood flow from the uterus through the vagina) occurs primarily in humans and close evolutionary relatives such as chimpanzees.Females of other species of placental mammal undergo estrous cycles, in which the endometrium is completely reabsorbed by the animal (covert menstruation) at the end of its reproductive cycle. This article focuses on the human menstrual cycle.

The menstrual cycle, under the control of the endocrine system, is necessary for reproduction. It is commonly divided into three phases: the follicular phase, ovulation, and the luteal phase; although some sources use a different set of phases: menstruation, proliferative phase, and secretory phase. The length of each phase varies from woman to woman and cycle to cycle, though the average menstrual cycle is 28 days. Menstrual cycles are counted from the first day of menstrual bleeding. Hormonal contraception interferes with the normal hormonal changes with the aim of preventing reproduction.

Stimulated by gradually increasing amounts of estrogen in the follicular phase, discharges of blood (= menses) slow then stop, and the lining of the uterus thickens. Follicles in the ovary begin developing under the influence of a complex interplay of hormones, and after several days one or occasionally two become dominant (non-dominant follicles atrophy and die). Approximately mid-cycle, 24–36 hours after the Luteinizing Hormone (LH) surges, the dominant follicle releases an ovum, or egg in an event called ovulation. After ovulation, the egg only lives for 24 hours or less without fertilization while the remains of the dominant follicle in the ovary become a corpus luteum; this body has a primary function of producing large amounts of progesterone. Under the influence of progesterone, the endometrium (uterine lining) changes to prepare for potential implantation of an embryo to establish a pregnancy. If implantation does not occur within approximately two weeks, the corpus luteum will involute, causing sharp drops in levels of both progesterone and estrogen. These hormone drops cause the uterus to shed its lining in a process termed menstruation.

In the menstrual cycle, changes occur in the female reproductive system as well as other systems (which lead to breast tenderness or mood changes, for example). A woman's first menstruation is termed menarche, and occurs typically around age 12. The end of a woman's reproductive phase is called the menopause, which commonly occurs somewhere between the ages of 45 and 55.

Terminology

The menarche is one of the later stages of puberty in girls. The average age of menarche in humans is 12 years, but is normal anywhere between ages 8 and 16. Factors such as heredity, diet and overall health can accelerate or delay menarche. The cessation of menstrual cycles at the end of a woman's reproductive period is termed menopause. The average age of menopause in women is 52 years in industrialised countries such as the UK, with anywhere between 45 and 55 being common. Menopause before age 45 is considered premature in industrialised countries. The age of menopause is largely a result of genetics; however, illnesses, certain surgeries, or medical treatments may cause menopause to occur earlier.

The length of a woman's menstrual cycle will typically vary, with some shorter cycles and some longer cycles. A woman who experiences variations of less than eight days between her longest cycles and shortest cycles is considered to have regular menstrual cycles. It is unusual for a woman to experience cycle length variations of less than four days. Length variation between eight and 20 days is considered as moderately irregular cycles. Variation of 21 days or more between a woman's shortest and longest cycle lengths is considered very irregular (see cycle abnormalities).

Phases

The menstrual cycle can be divided into several different phases. The average length of each phase is shown below, the first three are related to changes in the lining of the uterus whereas the final three are related to processes occurring in the ovary:

Name of phase Average start day

assuming a 28-day cycle Average end day

menstrual phase (menstruation) 1 4

proliferative phase (some sources include menstruation in this phase) 5 13

ischemic phase 27 28

follicular phase 1 13

ovulatory phase (ovulation) 13 16

luteal phase (also known as secretory phase) 16 28

Menstruation

Menstruation is also called menstrual bleeding, menses, catamenia or a period. The flow of menses normally serves as a sign that a woman has not become pregnant. (However, this cannot be taken as certainty, as a number of factors can cause bleeding during pregnancy; some factors are specific to early pregnancy, and some can cause heavy flow.) During the reproductive years, failure to menstruate may provide the first indication to a woman that she may have become pregnant.

Eumenorrhea denotes normal, regular menstruation that lasts for a few days (usually 3 to 5 days, but anywhere from 2 to 7 days is considered normal). The average blood loss during menstruation is 35 milliliters with 10–80 ml considered normal. (Because of this blood loss, women are more susceptible to iron deficiency than men are.)An enzyme called plasmin inhibits clotting in the menstrual fluid.

Painful cramping in the abdomen, back, or upper thighs is common during the first few days of menstruation (most women experience some pain during menstruation). Severe uterine pain during menstruation is known as dysmenorrhea, and it is most common among adolescents and younger women (affecting about 67.2% of adolescent females). When menstruation begins, symptoms of premenstrual syndrome (PMS) such as breast tenderness and irritability generally decrease. Many sanitary products are marketed to women for use during their menstruation.

Follicular phase

Reference ranges for estradiol and progesterone in the menstrual cycle, expressed in mass and molar concentration. The relative concentrations of estradiol and progesterone differ somewhat between the mass and molar scales because of slightly different molar mass. The scale is logarithmic.

Main article: Follicular phase

This phase is also called the proliferative phase because a hormone causes the lining of the uterus to grow, or proliferate, during this time.

Through the influence of a rise in follicle stimulating hormone (FSH) during the first days of the cycle, a few ovarian follicles are stimulated. These follicles, which were present at birth and have been developing for the better part of a year in a process known as folliculogenesis, compete with each other for dominance. Under the influence of several hormones, all but one of these follicles will stop growing, while one dominant follicle in the ovary will continue to maturity. The follicle that reaches maturity is called a tertiary, or Graafian, follicle, and it forms the ovum.

As they mature, the follicles secrete increasing amounts of estradiol, an estrogen. The estrogens initiate the formation of a new layer of endometrium in the uterus, histologically identified as the proliferative endometrium. The estrogen also stimulates crypts in the cervix to produce fertile cervical mucus, which may be noticed by women practicing fertility awareness.

Ovulation

An ovary about to release an egg.

During the follicular phase, estradiol suppresses production of luteinizing hormone (LH) from the anterior pituitary gland. When the egg has nearly matured, levels of estradiol reach a threshold above which they stimulate production of LH. These opposite responses of LH to estradiol may be enabled by the presence of two different estrogen receptors in the hypothalamus: estrogen receptor alpha, which is responsible for the negative feedback estradiol-LH loop, and estrogen receptor beta, which is responsible for the positive estradiol-LH relationship.In the average cycle this LH surge starts around cycle day 12 and may last 48 hours.

The release of LH matures the egg and weakens the wall of the follicle in the ovary, causing the fully developed follicle to release its secondary oocyte. The secondary oocyte promptly matures into an ootid and then becomes a mature ovum. The mature ovum has a diameter of about 0.2 mm.

Which of the two ovaries—left or right—ovulates appears essentially random; no known left and right co-ordination exists. Occasionally, both ovaries will release an egg; if both eggs are fertilized, the result is fraternal twins.

After being released from the ovary, the egg is swept into the fallopian tube by the fimbria, which is a fringe of tissue at the end of each fallopian tube. After about a day, an unfertilized egg will disintegrate or dissolve in the fallopian tube.

Fertilization by a spermatozoon, when it occurs, usually takes place in the ampulla, the widest section of the fallopian tubes. A fertilized egg immediately begins the process of embryogenesis, or development. The developing embryo takes about three days to reach the uterus and another three days to implant into the endometrium. It has usually reached the blastocyst stage at the time of implantation.

In some women, ovulation features a characteristic pain called mittelschmerz (German term meaning middle pain). The sudden change in hormones at the time of ovulation sometimes also causes light mid-cycle blood flow.

Luteal phase

Reference ranges for luteinizing hormone and follicle-stimulating hormone in the menstrual cycle, expressed in international units. The scale is logarithmic.

Main article: Luteal phase

The luteal phase is also called the secretory phase. An important role is played by the corpus luteum, the solid body formed in an ovary after the egg has been released from the ovary into the fallopian tube. This body continues to grow for some time after ovulation and produces significant amounts of hormones, particularly progesterone. Progesterone plays a vital role in making the endometrium receptive to implantation of the blastocyst and supportive of the early pregnancy; it also has the side effect of raising the woman's basal body temperature. There is a noted secretion of prolactin towards the end of the secretory phase.

After ovulation, the pituitary hormones FSH and LH cause the remaining parts of the dominant follicle to transform into the corpus luteum, which produces progesterone. The increased progesterone in the adrenals starts to induce the production of estrogen. The hormones produced by the corpus luteum also suppress production of the FSH and LH that the corpus luteum needs to maintain itself. Consequently, the level of FSH and LH fall quickly over time, and the corpus luteum subsequently atrophies.[3] Falling levels of progesterone trigger menstruation and the beginning of the next cycle. From the time of ovulation until progesterone withdrawal has caused menstruation to begin, the process typically takes about two weeks, with ten to sixteen days considered normal. For an individual woman, the follicular phase often varies in length from cycle to cycle; by contrast, the length of her luteal phase will be fairly consistent from cycle to cycle.

The loss of the corpus luteum can be prevented by fertilization of the egg; the resulting embryo produces human chorionic gonadotropin (hCG), which is very similar to LH and which can preserve the corpus luteum. Because the hormone is unique to the embryo, most pregnancy tests look for the presence of hCG.

Fertile window

The most fertile period (the time with the highest likelihood of pregnancy resulting from sexual intercourse) covers the time from some 5 days before until 1–2 days after ovulation. In an average 28 day cycle with a 14-day luteal phase, this corresponds to the second and the beginning of the third week. However, few cycles are exactly average. A variety of methods have been developed to help individual women estimate the relatively fertile and the relatively infertile days in the cycle: these systems are called fertility awareness.

Fertility awareness methods that rely on cycle length records alone are called calendar-based methods. Methods that require observation of one or more of the three primary fertility signs (basal body temperature, cervical mucus, and cervical position) are known as symptoms-based methods. Urine test kits are available that detect the LH surge that occurs 24 to 36 hours before ovulation; these are known as ovulation predictor kits (OPKs). Computerized devices that interpret basal body temperatures, urinary test results, or changes in saliva are called fertility monitors.

A woman's fertility is also affected by her age. As a woman's total egg supply is formed in fetal life,[30] to be ovulated decades later, it has been suggested that this long lifetime may make the chromatin of eggs more vulnerable to division problems, breakage, and mutation than the chromatin of sperm, which are produced continuously during a man's reproductive life.

Effect on other systems

Some women with neurological conditions experience increased activity of their conditions at about the same time during each menstrual cycle. For example, drops in estrogen levels have been known to trigger migraines (a neurological syndrome Migraines), especially when the woman who suffers migraines is also taking the birth control pill. Many women with epilepsy have more seizures in a pattern linked to the menstrual cycle; this is called "catamenial epilepsy". Different patterns seem to exist (such as seizures coinciding with the time of menstruation, or coinciding with the time of ovulation), and the frequency with which they occur has not been firmly established. Using one particular definition, one group of scientists found that around one-third of women with intractable partial epilepsy have catamenial epilepsy.An effect of hormones has been proposed, in which progesterone declines and estrogen increases would trigger seizures. Recently, studies have shown that high doses of estrogen can cause or worsen seizures, whereas high doses of progestrone can act like an antiepileptic drug. Studies by medical journals have found that women experiencing menses are 1.68 times more likely to commit suicide.

Mice have been used as an experimental system to investigate possible mechanisms by which levels of sex steroid hormones might regulate nervous system function. During the part of the mouse estrous cycle when progesterone is highest, the level of nerve-cell GABA receptor subtype delta was high. Since these GABA receptors are inhibitory, nerve cells with more delta receptors are less likely to fire than cells with lower numbers of delta receptors. During the part of the mouse estrous cycle when estrogen levels are higher than progesterone levels, the number of delta receptors decrease, increasing nerve cell activity, in turn increasing anxiety and seizure susceptibility.

Estrogen levels may affect thyroid behavior. For example, during the luteal phase (when estrogen levels are lower), the velocity of blood flow in the thyroid is lower than during the follicular phase (when estrogen levels are higher).

Among women living closely together, the onsets of menstruation may tend to synchronize somewhat. This McClintock effect was first described in 1971, and possibly explained by the action of pheromones in 1998. However, subsequent research has called this hypothesis into question.

Cycle abnormalities

Menstrual disorder

Infrequent or irregular ovulation is called oligoovulation. The absence of ovulation is called anovulation. Normal menstrual flow can occur without ovulation preceding it: an anovulatory cycle. In some cycles, follicular development may start but not be completed; nevertheless, estrogens will form and will stimulate the uterine lining. Anovulatory flow resulting from a very thick endometrium caused by prolonged, continued high estrogen levels is called estrogen breakthrough bleeding. Anovulatory bleeding triggered by a sudden drop in estrogen levels is called estrogen withdrawal bleeding. Anovulatory cycles commonly occur before menopause (perimenopause) and in women with polycystic ovary syndrome.

Very little flow (less than 10 ml) is called hypomenorrhea. Regular cycles with intervals of 21 days or fewer are polymenorrhea; frequent but irregular menstruation is known as metrorrhagia. Sudden heavy flows or amounts greater than 80 ml are termed menorrhagia. Heavy menstruation that occurs frequently and irregularly is menometrorrhagia. The term for cycles with intervals exceeding 35 days is oligomenorrhea.Amenorrhea refers to more than three to six months without menses (while not being pregnant) during a woman's reproductive years.

Ovulation suppression

Hormonal contraception

Half-used blister pack of a combined oral contraceptive. The white pills are placebos, mainly for the purpose of reminding the woman to continue taking the pills.

While some forms of birth control do not affect the menstrual cycle, hormonal contraceptives work by disrupting it. Progestogen negative feedback decreases the pulse frequency of gonadotropin-releasing hormone (GnRH) release by the hypothalamus, which decreases the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) by the anterior pituitary. Decreased levels of FSH inhibit follicular development, preventing an increase in estradiol levels. Progestogen negative feedback and the lack of estrogen positive feedback on LH release prevent a mid-cycle LH surge. Inhibition of follicular development and the absence of a LH surge prevent ovulation.

The degree of ovulation suppression in progestogen-only contraceptives depends on the progestogen activity and dose. Low dose progestogen-only contraceptives—traditional progestogen only pills, subdermal implants Norplant and Jadelle, and intrauterine system Mirena—inhibit ovulation in ~50% of cycles and rely mainly on other effects, such as thickening of cervical mucus, for their contraceptive effectiveness. Intermediate dose progestogen-only contraceptives—the progestogen-only pill Cerazette and the subdermal implant Implanon—allow some follicular development but more consistently inhibit ovulation in 97–99% of cycles. The same cervical mucus changes occur as with very low dose progestogens. High dose progestogen-only contraceptives—the injectables Depo-Provera and Noristerat—completely inhibit follicular development and ovulation.

Combined hormonal contraceptives include both an estrogen and a progestogen. Estrogen negative feedback on the anterior pituitary greatly decreases the release of FSH, which makes combined hormonal contraceptives more effective at inhibiting follicular development and preventing ovulation. Estrogen also reduces the incidence of irregular breakthrough bleeding. Several combined hormonal contraceptives—the pill, NuvaRing, and the contraceptive patch—are usually used in a way that causes regular withdrawal bleeding. In a normal cycle, menstruation occurs when estrogen and progesterone levels drop rapidly. Temporarily discontinuing use of combined hormonal contraceptives (a placebo week, not using patch or ring for a week) has a similar effect of causing the uterine lining to shed. If withdrawal bleeding is not desired, combined hormonal contraceptives may be taken continuously, although this increases the risk of breakthrough bleeding.

Lactational amenorrhea

Breastfeeding causes negative feedback to occur on pulse secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH). Depending on the strength of the negative feedback, breastfeeding women may experience complete suppression of follicular development, follicular development but no ovulation, or normal menstrual cycles may resume. Suppression of ovulation is more likely when suckling occurs more frequently. The production of prolactin in response to suckling is important to maintaining lactational amenorrhea. On average, women who are fully breastfeeding whose infants suckle frequently experience a return of menstruation at fourteen and a half months postpartum. There is a wide range of response between individual breastfeeding women, however, with some experiencing return of menstruation at two months and others remaining amenorrheic for up to 42 months postpartum.

Etymological and biological associations

Nightlighting and the moon

The word "menstruation" is etymologically related to "moon". The terms "menstruation" and "menses" are derived from the Latin mensis (month), which in turn relates to the Greek mene (moon) and to the roots of the English words month and moon— reflecting the fact that the moon's period of revolution around the earth (27.32 days) is similar to that of the human menstrual cycle. The synodical lunar month, the period between two new moons (or full moons), is 29.53 days long.

Some authors believe women in traditional societies without nightlighting ovulated with the full moon and menstruated with the new moon. A few studies in both humans and animals have found that artificial light at night does influence the menstrual cycle in humans and the estrus cycle in mice (cycles are more regular in the absence of artificial light at night), though none have demonstrated the synchronization of women's menstrual cycles with the lunar cycle. It has also been suggested that bright light exposure in the morning promotes more regular cycles. One author has suggested that sensitivity of women's cycles to nightlighting is caused by nutritional deficiencies of certain vitamins and minerals.

Other animals' menstrual cycles may be greatly different from lunar cycles: while the average cycle length in orangutans is the same as in humans—28 days—the average for chimpanzees is 35 days. Some take this as evidence that the average length of humans' cycle is most likely a coincidence.

Estrus and menstruation

Females of most mammal species advertise fertility to males with visual behavioral cues, pheromones, or both. This period of advertised fertility is known as estrus or heat. In species that experience estrus, females are generally only receptive to copulation while they are in heat(dolphins are an exception). In the estrous cycles of most placental mammals, if no fertilization takes place, the uterus reabsorbs the endometrium. This breakdown of the endometrium without vaginal discharge is sometimes called covert menstruation. Overt menstruation (where there is blood flow from the vagina) occurs primarily in humans and close evolutionary relatives such as chimpanzees. Some species, such as domestic dogs, experience small amounts of vaginal bleeding while in heat; this discharge has a different physiologic cause than menstruation.

A few mammals do not experience obvious, visible signs of fertility (concealed ovulation). In humans, while women can be taught to recognize their own level of fertility (fertility awareness), whether men can detect fertility in women is debated; recent studies have given conflicting results. Orangutans also lack visible signs of impending ovulation. Also, it has been said that the extended estrus period of the bonobo (reproductive-age females are in heat for 75% of their menstrual cycle) has a similar effect to the lack of a "heat" in human females.

(source:wikipedia)

Postnatal

Postnatal,

(Latin for 'after birth', from post meaning "after" and natalis meaning "of birth") is the period beginning immediately after the birth of a child and extending for about six weeks. Another term would be postpartum period, as it refers to the mother (whereas postnatal refers to the infant). Less frequently used is puerperium.

Biologically, it is the time after birth, a time in which the mother's body, including hormone levels and uterus size, returns to prepregnancy conditions. Lochia is post-partum vaginal discharge, containing blood, mucus, and placental tissue.

In scientific literature the term is commonly abbreviated to PX. So that 'day P5' should be read as 'the fifth day after birth'.

In newborns

During the first stages of this period, the newborn also starts his/her adaptation to extrauterine life, the most significant physiological transition until death.
The postpartum period in mothers

A woman in the Western world who is delivering in a hospital may leave the hospital as soon as she is medically stable and chooses to leave, which can be as early as a few hours postpartum, though the average for spontaneous vaginal delivery (SVD) is 1–2 days, and the average caesarean section postnatal stay is 3–4 days. During this time the mother is monitored for bleeding, bowel and bladder function, and baby care. The infant's health is also monitored.

Physical

Further information: Sex after pregnancy

The mother is assessed for tears, and is sutured if necessary. Also, she may suffer from constipation or hemorrhoids, both of which would be managed. The bladder is also assessed for infection, retention and any problems in the muscles.

The major focus of postpartum care is ensuring that the mother is healthy and capable of taking care of her newborn, equipped with all the information she needs about breastfeeding, reproductive health and contraception, and the imminent life adjustment.

Some medical conditions may occur in the postpartum period, such as Sheehan syndrome and peripartum cardiomyopathy.

In some cases, this adjustment is not made easily, and women may suffer from postpartum depression, posttraumatic stress disorder or even puerperal psychosis.

Psychological

Early detection and adequate treatment is required. Approximately 25% - 85% of postpartum women will experience the "blues" for a few days. Between 7% - 17% may experience clinical depression, with a higher risk among those women with a history of clinical depression. Rarely, in 1 in 1,000 cases, women experience a psychotic episode, again with a higher risk among those women with pre-existing mental illness. Despite the wide spread myth of hormonal involvement, repeated studies have not linked hormonal changes with postpartum psychological symptoms. Rather, these are symptoms of a pre-existing mental illness, exacerbated by fatigue, changes in schedule and other common parenting stressors. 

Over 1 in 100 women develop Posttraumatic stress disorder following childbirth, many more suffer from one or more of the symptoms. PTSD may occur after severe complications during delivery, but personality characteristics and previous psychiatric illness has also been associated with the development of posttraumatic stress symptoms.

Postpartum psychosis (also known as puerperal psychosis), is a more severe form of mental illness than postpartum depression, with an indicence of approximately 0.2%.

Cultures

In East Asia

In some East Asian cultures, such as Chinese and Vietnamese, there is a traditional custom of postpartum confinement known in English as doing the month or sitting the month (Mandarin zuò yuèzi 坐月子). Confinement traditionally lasts 30 days[3], although regional variants may last 40, 60 or as many as 100 days[citation needed]. This tradition combines prescribed foods with a number of restrictions on activities considered to be harmful. It is widely believed in many East Asian societies that this custom helps heal injuries to the perineum, promote the contraction of the uterus, and promote lactation. 

[edit]In India

In Hindu culture, the puerperium was traditionally considered a period of relative impurity (asaucham) due to the processes of childbirth, and a period of confinement of 10 days (known as sutakam) was recommended for the mother. During this period, she was exempted from usual household chores and religious rites. The father was purified by a ritual bath after visiting the mother in confinement. In the event of a stillbirth, the period of impurity for both parents was 24 hours. 

(source:wikipedia)

Abortion

From Wikipedia, the free encyclopedia

Induced abortion
Classification and external resources
Bas-relief at Angkor Wat, Cambodia, c. 1150, depicting a demon inducing an abortion by pounding the abdomen of a pregnant woman with a pestle.
ICD-10	O04.
ICD-9	779.6
DiseasesDB	4153
MedlinePlus	002912
eMedicine	article/252560

Abortion is the termination of a pregnancy by the removal or expulsion from the uterus of a fetusor embryo, resulting in or caused by its death. An abortion can occur spontaneously due tocomplications during pregnancy or can be induced, in humans and other species. In the context of human pregnancies, an abortion induced to preserve the health of the gravida (pregnant female) is termed a therapeutic abortion, while an abortion induced for any other reason is termed an elective abortion. The term abortion most commonly refers to the induced abortion of a human pregnancy, while spontaneous abortions are usually termed miscarriages.

Worldwide 42 million abortions are estimated to take place annually with 22 million of these occurring safely and 20 million unsafely. While maternal mortality seldom results from safe abortions, unsafe abortions result in 70,000 deaths and 5 million disabilities per year.One of the main determinants of the availability of safe abortions is the legality of the procedure. Forty percent of the world's women are able to access therapeutic and elective abortions within gestational limits. The frequency of abortions is, however, similar whether or not access is restricted.

Abortion has a long history and has been induced by various methods including herbalabortifacients, the use of sharpened tools, physical trauma, and other traditional methods. Contemporary medicine utilizes medications and surgical procedures to induce abortion. Thelegality, prevalence, and cultural views on abortion vary substantially around the world. In many parts of the world there is prominent and divisive public controversy over the ethical and legal issues of abortion. Abortion and abortion-related issues feature prominently in the national politics in many nations, often involving the opposing pro-life and pro-choice worldwide social movements (both self-named). Incidence of abortion has declined worldwide, as access to family planning education and contraceptive services has increased.

Types

A 10-week-old fetus removed via a therapeutic abortion from a 44-year-old female diagnosed with early-stage uterine cancer. The uterus (womb), included the fetus.

Spontaneous
Miscarriage

Spontaneous abortion (also known as miscarriage) is the expulsion of an embryo or fetus due to accidental trauma or natural causes before approximately the 22nd week of gestation; the definition by gestational age varies by country. Most miscarriages are due to incorrect replication of chromosomes; they can also be caused by environmental factors. A pregnancy that ends before 37 weeks of gestation resulting in a live-born infant is known as a "premature birth". When a fetus dies in utero after about 22 weeks, or during delivery, it is usually termed "stillborn". Premature births and stillbirths are generally not considered to be miscarriages although usage of these terms can sometimes overlap.

Between 10% and 50% of pregnancies end in clinically apparent miscarriage, depending upon the age and health of the pregnant woman. Most miscarriages occur very early in pregnancy, in most cases, they occur so early in the pregnancy that the woman is not even aware that she was pregnant. One study testing hormones for ovulation and pregnancy found that 61.9% of conceptuses were lost prior to 12 weeks, and 91.7% of these losses occurred subclinically, without the knowledge of the once pregnant woman.

The risk of spontaneous abortion decreases sharply after the 10th week from the last menstrual period (LMP). One study of 232 pregnant women showed "virtually complete [pregnancy loss] by the end of the embryonic period" (10 weeks LMP) with a pregnancy loss rate of only 2 percent after 8.5 weeks LMP.

The most common cause of spontaneous abortion during the first trimester is chromosomal abnormalities of the embryo/fetus, accounting for at least 50% of sampled early pregnancy losses.Other causes include vascular disease (such as lupus), diabetes, other hormonal problems, infection, and abnormalities of the uterus. Advancing maternal age and a patient history of previous spontaneous abortions are the two leading factors associated with a greater risk of spontaneous abortion. A spontaneous abortion can also be caused by accidental trauma; intentional trauma or stress to cause miscarriage is considered induced abortion or feticide.

Induced

A pregnancy can be intentionally aborted in many ways. The manner selected depends chiefly upon the gestational age of the embryo or fetus, which increases in size as it ages.Specific procedures may also be selected due to legality, regional availability, and doctor-patient preference. Reasons for procuring induced abortions are typically characterized as either therapeutic or elective. An abortion is medically referred to as therapeutic when it is performed to:

save the life of the pregnant woman;

preserve the woman's physical or mental health;

terminate pregnancy that would result in a child born with a congenital disorder that would be fatal or associated with significant morbidity; or

selectively reduce the number of fetuses to lessen health risks associated with multiple pregnancy.

An abortion is referred to as elective when it is performed at the request of the woman "for reasons other than maternal health or fetal disease."

Methods

Gestational age may determine which abortion methods are practiced.
Medical abortion

"Medical abortions" are non-surgical abortions that use pharmaceutical drugs. Medical abortions comprise 10% of all abortions in the United States and Europe.[citation needed] Combined regimens include methotrexate or mifepristone, followed by a prostaglandin (either misoprostol or gemeprost: misoprostol is used in the U.S.; gemeprost is used in the UK and Sweden.) When used within 49 days gestation, approximately 92% of women undergoing medical abortion with a combined regimen completed it without surgical intervention.Misoprostol can be used alone, but has a lower efficacy rate than combined regimens. In cases of failure of medical abortion, vacuum or manual aspiration is used to complete the abortion surgically.

Surgical

A vacuum aspiration abortion at eight weeks gestational age (six weeks after fertilization).

1: Amniotic sac

2: Embryo

3: Uterine lining

4: Speculum

5: Vacurette

6: Attached to a suction pump

In the first 12 weeks, suction-aspiration or vacuum abortion is the most common method. Manual vacuum aspiration (MVA) abortion consists of removing the fetus or embryo, placenta and membranes by suction using a manual syringe, while electric vacuum aspiration (EVA) abortion uses an electric pump. These techniques are comparable, and differ in the mechanism used to apply suction, how early in pregnancy they can be used, and whether cervical dilation is necessary. MVA, also known as "mini-suction" and "menstrual extraction", can be used in very early pregnancy, and does not require cervical dilation. Surgical techniques are sometimes referred to as 'Suction (or surgical) Termination Of Pregnancy' (STOP). From the 15th week until approximately the 26th, dilation and evacuation (D&E) is used. D&E consists of opening the cervix of the uterus and emptying it using surgical instruments and suction.

Dilation and curettage (D&C), the second most common method of abortion, is a standard gynecological procedure performed for a variety of reasons, including examination of the uterine lining for possible malignancy, investigation of abnormal bleeding, and abortion. Curettage refers to cleaning the walls of the uterus with a curette. The World Health Organization recommends this procedure, also called sharp curettage, only when MVA is unavailable.

Other techniques must be used to induce abortion in the second trimester. Premature delivery can be induced with prostaglandin; this can be coupled with injecting the amniotic fluid with hypertonic solutions containing saline or urea. After the 16th week of gestation, abortions can be induced by intact dilation and extraction (IDX) (also called intrauterine cranial decompression), which requires surgical decompression of the fetus's head before evacuation. IDX is sometimes called "partial-birth abortion," which has been federally banned in the United States. A hysterotomy abortion is a procedure similar to a caesarean section and is performed under general anesthesia. It requires a smaller incision than a caesarean section and is used during later stages of pregnancy.

From the 20th to 23rd week of gestation, an injection to stop the fetal heart may be used as the first phase of the surgical abortion procedure to ensure that the fetus is not born alive.

Other methods

Historically, a number of herbs reputed to possess abortifacient properties have been used in folk medicine: tansy, pennyroyal, black cohosh, and the now-extinct silphium (see history of abortion).The use of herbs in such a manner can cause serious—even lethal—side effects, such as multiple organ failure, and is not recommended by physicians.

Abortion is sometimes attempted by causing trauma to the abdomen. The degree of force, if severe, can cause serious internal injuries without necessarily succeeding in inducing miscarriage. Both accidental and deliberate abortions of this kind can be subject to criminal liability in many countries. In Southeast Asia, there is an ancient tradition of attempting abortion through forceful abdominal massage. One of the bas reliefs decorating the temple of Angkor Wat in Cambodia depicts a demon performing such an abortion upon a woman who has been sent to the underworld.
Reported methods of unsafe, self-induced abortion include misuse of misoprostol, and insertion of non-surgical implements such as knitting needles and clothes hangers into the uterus. These methods are rarely seen in developed countries where surgical abortion is legal and available.

Health risks

See also: Health risks of unsafe abortion

Abortion, when legally performed in developed countries, is among the safest procedures in medicine. In such settings, risk of maternal death is between 0.2–1.2 per 100,000 procedures. In comparison, by 1996, mortality from childbirth in developed countries was 11 times greater. Unsafe abortions (defined by the World Health Organization as those performed by unskilled individuals, with hazardous equipment, or in unsanitary facilities) carry a high risk of maternal death and other complications. For unsafe procedures, the mortality rate has been estimated at 367 per 100,000.

Physical health

Surgical abortion methods, like most minimally invasive procedures, carry a small potential for serious complications.

Surgical abortion is generally safe and the rate of major complications is low but varies depending on how far pregnancy has progressed and the surgical method used.Concerning gestational age, incidence of major complications is highest after 20 weeks of gestation and lowest before the 8th week.With more advanced gestation there is a higher risk of uterine perforation and retained products of conception,and specific procedures like dilation and evacuation may be required.

Concerning the methods used, general incidence of major complications for surgical abortion varies from lower for suction curettage, to higher for saline instillation.Possible complications include hemorrhage, incomplete abortion, uterine or pelvic infection, ongoing intrauterine pregnancy, misdiagnosed/unrecognized ectopic pregnancy, hematometra (in the uterus), uterine perforation and cervical laceration. Use of general anesthesia increases the risk of complications because it relaxes uterine musculature making it easier to perforate.

In the first trimester, health risks associated with medical abortion are generally considered no greater than for surgical abortion.

Abortion and mental health

No scientific research has demonstrated that abortion is a cause of poor mental health in the general population. However there are groups of women who may be at higher risk of coping with problems and distress following abortion. Some factors in a woman's life, such as emotional attachment to the pregnancy, lack of social support, pre-existing psychiatric illness, and conservative views on abortion increase the likelihood of experiencing negative feelings after an abortion. The American Psychological Association (APA) concluded that abortion does not lead to increased mental health problems.

Some proposed negative psychological effects of abortion have been referred to by anti-abortion advocates as a separate condition called "post-abortion syndrome." However, the existence of "post-abortion syndrome" is not recognized by any medical or psychological organization.

Incidence

The number of abortions performed worldwide has deceased between 1995 and 2003 from 45.6 million to 41.6 million (a decrease from 35 to 29 per 1000 women between 15 and 44 years of age). The greatest decrease has occurred in the developed world with a decrease from 39 to 26 per 1000 women in comparison to the developing world which had a decrease from 34 to 29 per 1000 women. Of these approximately 42 million abortions 22 million occurred safely and 20 million unsafely.

The incidence and reasons for induced abortion vary regionally. Some countries, such as Belgium (11.2 per 1000 known pregnancies) and the Netherlands (10.6 per 1000), had a comparatively low rate of induced abortion, while others like Russia (62.6 per 1000) and Vietnam (43.7 per 1000) had a high rate. The world ratio was 26 induced abortions per 1000 known pregnancies (excluding miscarriages and stillbirths).
By gestational age and method

Histogram of abortions by gestational age in England and Wales during 2004. Average is 9.5 weeks. (left) Abortion in the United States by gestational age, 2004. (Data source: Centers for Disease Control and Prevention) (right)

Abortion rates also vary depending on the stage of pregnancy and the method practiced. In 2003, from data collected in those areas of the United States that sufficiently reported gestational age, it was found that 88.2% of abortions were conducted at or prior to 12 weeks, 10.4% from 13 to 20 weeks, and 1.4% at or after 21 weeks. 90.9% of these were classified as having been done by "curettage" (suction-aspiration, Dilation and curettage, Dilation and evacuation), 7.7% by "medical" means (mifepristone), 0.4% by "intrauterine instillation" (saline or prostaglandin), and 1.0% by "other" (including hysterotomy and hysterectomy). The Guttmacher Institute estimated there were 2,200 intact dilation and extraction procedures in the U.S. during 2000; this accounts for 0.17% of the total number of abortions performed that year.Similarly, in England and Wales in 2006, 89% of terminations occurred at or under 12 weeks, 9% between 13 to 19 weeks, and 1.5% at or over 20 weeks. 64% of those reported were by vacuum aspiration, 6% by D&E, and 30% were medical. Later abortions are more common in China, India, and other developing countries than in developed countries.

By personal and social factors

A bar chart depicting selected data from the 1998 AGI meta-study on the reasons women stated for having an abortion.

A 1998 aggregated study, from 27 countries, on the reasons women seek to terminate their pregnancies concluded that common factors cited to have influenced the abortion decision were: desire to delay or end childbearing, concern over the interruption of work or education, issues of financial or relationship stability, and perceived immaturity.A 2004 study in which American women at clinics answered a questionnaire yielded similar results. In Finland and the United States, concern for the health risks posed by pregnancy in individual cases was not a factor commonly given; however, in Bangladesh, India, and Kenya health concerns were cited by women more frequently as reasons for having an abortion. 1% of women in the 2004 survey-based U.S. study became pregnant as a result of rape and 0.5% as a result of incest. Another American study in 2002 concluded that 54% of women who had an abortion were using a form of contraception at the time of becoming pregnant while 46% were not. Inconsistent use was reported by 49% of those using condoms and 76% of those using the combined oral contraceptive pill; 42% of those using condoms reported failure through slipping or breakage.The Guttmacher Institute estimated that "most abortions in the United States are obtained by minority women" because minority women "have much higher rates of unintended pregnancy."

Some abortions are undergone as the result of societal pressures. These might include the stigmatization of disabled people, preference for children of a specific sex, disapproval of single motherhood, insufficient economic support for families, lack of access to or rejection of contraceptive methods, or efforts toward population control (such as China's one-child policy). These factors can sometimes result in compulsory abortion or sex-selective abortion.

Unsafe abortion

Soviet poster circa 1925, promoting hospital abortions. Title translation: "Abortions performed by either trained or self-taught midwives not only maim the woman, they also often lead to death."

Women seeking to terminate their pregnancies sometimes resort to unsafe methods, particularly where and when access to legal abortion is restricted. The World Health Organization (WHO) defines an unsafe abortion as being "a procedure ... carried out by persons lacking the necessary skills or in an environment that does not conform to minimal medical standards, or both." Unsafe abortions are sometimes known colloquially as "back-alley" abortions. They may be performed by the woman herself, another person without medical training, or a professional health provider operating in sub-standard conditions. Unsafe abortion remains a public health concern due to the higher incidence and severity of its associated complications, such as incomplete abortion, sepsis, hemorrhage, and damage to internal organs. It is estimated that 20 million unsafe abortions occur around the world annually and that 70,000 of these result in the woman's death.Complications of unsafe abortion are said to account, globally, for approximately 13% of all maternal mortalities, with regional estimates including 12% in Asia, 25% in Latin America, and 13% in sub-Saharan Africa.Although the global rate of abortion declined from 45.6 million in 1995 to 41.6 million in 2003, unsafe procedures still accounted for 48% of all abortions performed in 2003.Health education, access to family planning, and improvements in health care during and after abortion have been proposed to address this phenomenon.

History

"French Periodical Pills." An example of a clandestine advertisement published in an 1845 edition of the Boston Daily Times.

History of abortion

Induced abortion can be traced to ancient times.There is evidence to suggest that, historically, pregnancies were terminated through a number of methods, including the administration of abortifacient herbs, the use of sharpened implements, the application of abdominal pressure, and other techniques.

The Hippocratic Oath, the chief statement of medical ethics for Hippocratic physicians in Ancient Greece, forbade doctors from helping to procure an abortion by pessary. Soranus, a second-century Greek physician, suggested in his work Gynaecology that women wishing to abort their pregnancies should engage in energetic exercise, energetic jumping, carrying heavy objects, and riding animals. He also prescribed a number of recipes for herbal baths, pessaries, and bloodletting, but advised against the use of sharp instruments to induce miscarriage due to the risk of organ perforation.It is also believed that, in addition to using it as a contraceptive, the ancient Greeks relied upon silphium as an abortifacient. Such folk remedies, however, varied in effectiveness and were not without risk. Tansy and pennyroyal, for example, are two poisonous herbs with serious side effects that have at times been used to terminate pregnancy.

During the medieval period, physicians in the Islamic world documented detailed and extensive lists of birth control practices, including the use of abortifacients, commenting on their effectiveness and prevalence.They listed many different birth control substances in their medical encyclopedias, such as Avicenna listing 20 in The Canon of Medicine (1025) and Muhammad ibn Zakariya ar-Razi listing 176 in his Hawi (10th century). This was unparalleled in European medicine until the 19th century.

During the Middle Ages, abortion was tolerated and there were no laws against it.A medieval female physician, Trotula of Salerno, administered a number of remedies for the “retention of menstrua,” which was sometimes a code for early abortifacients. Pope Sixtus V (1585–90) is noted as the first Pope to declare that abortion is homicide regardless of the stage of pregnancy.Abortion in the 19th century continued, despite bans in both the United Kingdom and the United States, as the disguised, but nonetheless open, advertisement of services in the Victorian era suggests.

In the 20th century the Soviet Union (1919), Iceland (1935) and Sweden (1938) were among the first countries to legalize certain or all forms of abortion. In 1935 Nazi Germany, a law was passed permitting abortions for those deemed "hereditarily ill," while women considered of German stock were specifically prohibited from having abortions.

Society and culture

Abortion debate

Pro-choice activists near the Washington Monument at the March for Women's Lives in 2004. (left) Pro-life activists near the Washington Monument at the annual 2009 March for Life in Washington, DC. (right)

Main article: Abortion debate

In the history of abortion, induced abortion has been the source of considerable debate, controversy, and activism. An individual's position on the complex ethical, moral, philosophical, biological, and legal issues is often related to his or her value system. The main positions are one that argues in favor of access to abortion and one argues against access to abortion. Opinions of abortion may be described as being a combination of beliefs on its morality, and beliefs on the responsibility, ethical scope, and proper extent of governmental authorities in public policy. Religious ethics also has an influence upon both personal opinion and the greater debate over abortion (see religion and abortion).

Abortion debates, especially pertaining to abortion laws, are often spearheaded by groups advocating one of these two positions. In the United States, those in favor of greater legal restrictions on, or even complete prohibition of abortion, most often describe themselves as pro-life while those against legal restrictions on abortion describe themselves as pro-choice. Generally, the former position argues that a human fetus is a human being with a right to live making abortion tantamount to murder. The latter position argues that a woman has certain reproductive rights, especially the choice whether or not to carry a pregnancy to term.

In both public and private debate, arguments presented in favor of or against abortion access focus on either the moral permissibility of an induced abortion, or justification of laws permitting or restricting abortion.

Debate also focuses on whether the pregnant woman should have to notify and/or have the consent of others in distinct cases: a minor, her parents; a legally married or common-law wife, her husband; or a pregnant woman, the biological father. In a 2003 Gallup poll in the United States, 79% of male and 67% of female respondents were in favor of legalized mandatory spousal notification; overall support was 72% with 26% opposed.

Abortion law

Main article: Abortion law

Reproductive rights

International status of abortion law:

Legal on request

Legal for maternal life, health, mental health, rape, fetal defects, and/or socioeconomic factors

Legal for or illegal with exception for maternal life, health, mental health, rape, and/or fetal defects

Illegal with exception for maternal life, health, mental health and/or rape

Illegal with exception for maternal life, health, and/or mental health

Illegal with no exceptions

No information

Vertical stripes (various colours): Illegal but unenforced

Before the scientific discovery in the nineteenth century that human development begins at fertilization, English common law forbade abortions after "quickening", that is, after "an infant is able to stir in the mother's womb." There was also an earlier period in England when abortion was prohibited "if the foetus is already formed" but not yet quickened. Both pre- and post-quickening abortions were criminalized by Lord Ellenborough's Act in 1803. In 1861, the Parliament of the United Kingdom passed the Offences against the Person Act 1861, which continued to outlaw abortion and served as a model for similar prohibitions in some other nations.

The Soviet Union, with legislation in 1920, and Iceland, with legislation in 1935, were two of the first countries to generally allow abortion. The second half of the 20th century saw the liberalization of abortion laws in other countries. The Abortion Act 1967 allowed abortion for limited reasons in the United Kingdom (except Northern Ireland). In the 1973 case, Roe v. Wade, the United States Supreme Court struck down state laws banning abortion, ruling that such laws violated an implied right to privacy in the United States Constitution. The Supreme Court of Canada, similarly, in the case of R. v. Morgentaler, discarded its criminal code regarding abortion in 1988, after ruling that such restrictions violated the security of person guaranteed to women under the Canadian Charter of Rights and Freedoms. Canada later struck down provincial regulations of abortion in the case of R. v. Morgentaler (1993). By contrast, abortion in Ireland was affected by the addition of an amendment to the Irish Constitution in 1983 by popular referendum, recognizing "the right to life of the unborn".

Current laws pertaining to abortion are diverse. Religious, moral, and cultural sensibilities continue to influence abortion laws throughout the world. The right to life, the right to liberty, the right to security of person, and the right to reproductive health are major issues of human rights that are sometimes used as justification for the existence or absence of laws controlling abortion. Many countries in which abortion is legal require that certain criteria be met in order for an abortion to be obtained, often, but not always, using a trimester-based system to regulate the window of legality:

In the United States, some states impose a 24-hour waiting period before the procedure, prescribe the distribution of information on fetal development, or require that parents be contacted if their minor daughter requests an abortion.

In the United Kingdom, as in some other countries, two doctors must first certify that an abortion is medically or socially necessary before it can be performed.

In Canada, a similar requirement was rejected as unconstitutional in 1988.

Other countries, in which abortion is normally illegal, will allow one to be performed in the case of rape, incest, or danger to the pregnant woman's life or health.

A few nations ban abortion entirely: Chile, El Salvador, Malta, and Nicaragua, with consequent rises in maternal death directly and indirectly due to pregnancy. However, in 2006, the Chilean government began the free distribution of emergency contraception.

In Bangladesh, abortion is illegal, but the government has long supported a network of "menstrual regulation clinics", where menstrual extraction (manual vacuum aspiration) can be performed as menstrual hygiene.

In places where abortion is illegal or carries heavy social stigma, pregnant women may engage in medical tourism and travel to countries where they can terminate their pregnancies. Women without the means to travel can resort to providers of illegal abortions or try to do it themselves. 

In the US, about 8% of abortions are performed on women who travel from another state.However, that is driven at least partly by differing limits on abortion according to gestational age or the scarcity of doctors trained and willing to do later abortions.

Sex-selective abortion

Sonography and amniocentesis allow parents to determine sex before childbirth. The development of this technology has led to sex-selective abortion, or the targeted termination of female fetuses.

It is suggested that sex-selective abortion might be partially responsible for the noticeable disparities between the birth rates of male and female children in some places. The preference for male children is reported in many areas of Asia, and abortion used to limit female births has been reported in China, Taiwan, South Korea, and India.

In India, the economic role of men, the costs associated with dowries, and a common Indian tradition which dictates that funeral rites must be performed by a male relative have led to a cultural preference for sons. The widespread availability of diagnostic testing, during the 1970s and '80s, led to advertisements for services which read, "Invest 500 rupees [for a sex test] now, save 50,000 rupees [for a dowry] later."In 1991, the male-to-female sex ratio in India was skewed from its biological norm of 105 to 100, to an average of 108 to 100. Researchers have asserted that between 1985 and 2005 as many as 10 million female fetuses may have been selectively aborted. The Indian government passed an official ban of pre-natal sex screening in 1994 and moved to pass a complete ban of sex-selective abortion in 2002.

In the People's Republic of China, there is also a historic son preference. The implementation of the one-child policy in 1979, in response to population concerns, led to an increased disparity in the sex ratio as parents attempted to circumvent the law through sex-selective abortion or the abandonment of unwanted daughters. Sex-selective abortion might be an influence on the shift from the baseline male-to-female birth rate to an elevated national rate of 117:100 reported in 2002. The trend was more pronounced in rural regions: as high as 130:100 in Guangdong and 135:100 in Hainan. A ban upon the practice of sex-selective abortion was enacted in 2003.

In other animals

Further information: Miscarriage#In other animals

Spontaneous abortion occurs in various animals. For example, in sheep, it may be caused by crowding through doors, or being chased by dogs. In cows, abortion may be caused by contagious disease, such as Brucellosis or Campylobacter, but can often be controlled by vaccination. Additionally, many other diseases are known to increase the risk of miscarriage in humans and other animals.[citation needed]

Abortion may also be induced in animals, in the context of animal husbandry. For example, abortion may be induced in mares that have been mated improperly, or that have been purchased by owners who did not realize the mares were pregnant, or that are pregnant with twin foals.

Feticide can occur in horses and zebras due to male harassment of pregnant mares or forced copulation, although the frequency in the wild has been questioned. Male Gray langur monkeys may attack females following male takeover, causing miscarriage.

(source:wikipedia)

Drugs in pregnancy

Drugs used during pregnancy,

can have temporary or permanent effects on the fetus. Any drug that acts during embryonic or fetal development to produce a permanent alteration of form or function is known as a teratogen.

for the pregnant woman

Many physicians would prefer not to prescribe for pregnant women, the major concern being over teratogenicity of the drugs. The apprehension is not necessarily data driven and is mostly due to lack of clinical studies in pregnant women. This can result in inappropriate treatment of pregnant women and fetus. Use of drugs in pregnancy is not always wrong. For example, high fever is harmful for the fetus in the early months, thus the use of paracetamol (acetaminophen) is generally associated with lower risk than the fever itself. Similarly, diabetes mellitus during pregnancy may need intensive therapy with insulin to prevent complications to mother and baby.

Period of drug use

Pregnancy and development of fetus progresses through various changes. The period of one week from fertilisation to implantation of the fertilized egg is called preimplantation period. This is an 'all or none' period, .i.e an insult can either cause death or complete recovery. The period from the 8th day to the end of 8th week (2nd month) is the period of organogenesis during which the organs are formed in the fetus. This is the most crucial time with regard to 'structural malformations' and concern over teratogenicity of drugs. From the 3rd month week to the end of 9 months is the period of fetal maturation. Intake of drugs during this period may modify the 'function' of the fetal organs rather than causing gross structural malformations in the fetus, for example, aminoglycosides can affect the functioning of kidneys and also the hearing mechanism.

Categories of drugs

The Food and Drug Administration (FDA) has developed a rating system to provide therapeutic guidance based on potential benefits and fetal risks. Drugs have been classified into categories A, B, C, D and X based on this system of classification. Drugs like multivitamins that have demonstrated no fetal risks after controlled studies in humans are classified as Category A. On the other hand drugs like thalidomide with proven fetal risks that outweigh all benefits are classified as Category X.

Classification of a few important drugs/vaccines

Antibacterial agents

Category B : Penicillin, metronidazole, nitrofurantoin, cephalosporins, clindamycin, terbinafine, some macrolides e.g. azithromycin, erythromycin

Category C : Some aminoglycosides, chloroquine, quinolones, mebendazole, fluconazole

Category D : Tetracyclines, gentamicin, tobramycin

Cardiovascular drugs

Category B : Heparin (LMW)

Category C : Heparin (conventional), beta-blockers, (dihydropyridine) calcium antagonists, furosemide, digoxin, methyldopa

Category D : ACE inhibitors, ARBs, coumarins, thiazides, diltiazem

Central nervous system drugs

Category B : Acetaminophen, caffeine

Category C : Aspirin, clonidine, rofecoxib

Category D : Carbamezapine, valproic acid, diazepam, lithium

Vaccines

Category C : Tetanus toxoid, polio vaccine , BCG vaccine, hepatitis A vaccine, hepatitis B vaccine and rabies vaccine.

(source:wikipedia)

Immune tolerance in pregnancy

Immune tolerance in pregnancy, or gestational immune tolerance,

is the absence of a maternal immune response against the fetus and placenta, which thus may be viewed as unusually successful allografts, since they genetically differ from the mother.In the same way, many cases of spontaneous abortion may be described in the same way as maternal transplant rejection.

Mechanisms

Placental mechanisms

The placenta functions as an immunological barrier between the mother and the fetus.

The placenta functions as an immunological barrier between the mother and the fetus, creating an immunologically privileged site. For this purpose, it uses several mechanisms:

It secretes Neurokinin B containing phosphocholine molecules. This is the same mechanism used by parasitic nematodes to avoid detection by the immune system of their host.

Also, there is presence of small lymphocytic suppressor cells in the fetus that inhibit maternal cytotoxic T cells by inhibiting the response to interleukin 2.

The placental trophoblast cells do not express the classical MHC class I isotypes HLA-A and HLA-B, unlike most other cells in the body, and this absence is assumed to prevent destruction by maternal cytotoxic T cells, which otherwise would recognize the fetal HLA-A and HLA-B molecules as foreign. On the other hand, they do express the atypical MHC class I isotypes HLA-E and HLA-G, which is assumed to prevent destruction by maternal NK cells, which otherwise destruct cells that do not express any MHC class I.However, trophoblast cells do express the rather typical HLA-C.

It forms a syncytium without any extracellular spaces between cells in order to limit the exchange of migratory immune cells between the developing embryo and the body of the mother (something an epithelium will not do sufficiently, as certain blood cells are specialized to be able to insert themselves between adjacent epithelial cells). The fusion of the cells is apparently caused by viral fusion proteins from endosymbiotic endogenous retrovirus (ERV). [4] An immunoevasive action was the initial normal behavior of the viral protein, in order to avail for the virus to spread to other cells by simply merging them with the infected one. It is believed that the ancestors of modern viviparous mammals evolved after an infection by this virus, enabling the fetus to better resist the immune system of the mother.

Still, the placenta does allow maternal IgG antibodies to pass from to the fetus to protect it against infections. However, these antibodies do not target fetal cells, unless any fetal material has escaped across the placenta where it can come in contact with maternal B cells and make those B cells start to produce antibodies against fetal targets. The mother does produce antibodies against foreign ABO blood types, where the fetal blood cells are possible targets, but these preformed antibodies are of the IgM type,and do not cross the placenta.

Other mechanisms

Still, the placental barrier is not the sole means to evade the immune system, as foreign fetal cells also persist in the maternal circulation, on the other side of the placental barrier.

In any case, the placenta does not block maternal IgG antibodies, which thereby may pass through the human placenta, providing immune protection to the fetus against infectious diseases.

One model for the induction of tolerance during the very early stages of pregnancy is the Eutherian Fetoembryonic Defense System (eu-FEDS) hypothesis. The basic premise of the eu-FEDS hypothesis is that both soluble and cell surface associated glycoproteins, present in the reproductive system and expressed on gametes, suppress any potential immune responses, and inhibit rejection of the fetus . The eu-FEDS model further suggests that specific carbohydrate sequences (oligosaccharides) are covalently linked to these immunosuppressive glycoproteins and act as “functional groups” that suppress the immune response. The major uterine and fetal glycoproteins that are associated with the eu-FEDS model in the human include alpha-fetoprotein, CA125, and glycodelin-A (also known as placental protein 14 (PP14)).

Regulatory T cells also likely play a role.[9].

Also, a shift from cell-mediated immunity toward humoral immunity is believed to occur.

Insufficient tolerance

Many cases of spontaneous abortion may be described in the same way as maternal transplant rejection. Other examples of insufficient immune tolerance in pregnancy are Rh disease and pre-eclampsia:

Rh disease is caused by the mother producing antibodies (including IgG antibodies) against the Rhesus D antigen on her baby's red blood cells. It occurs if the mother is Rh negative and the baby is Rh positive, and a small amount of Rh positive blood from any previous pregnancy has entered the mother's circulation to make her produce IgG antibodies against the Rhesus D antigen. Maternal IgG is able to pass through the placenta into the fetus and if the level of it is sufficient, it will cause destruction of Rhesus D positive fetal red blood cells leading to development Rh disease. Generally Rhesus disease becomes worse with each additional Rhesus incompatible pregnancy.

One cause of pre-eclampsia is an abnormal immune response towards the placenta. There is substantial evidence for exposure to partner's semen as prevention for pre-eclampsia, largely due to the absorption of several immune modulating factors present in seminal fluid.

Increased infectious susceptibility

The immunologic changes in pregnancy alters the susceptibility to and severity of infectious diseases. For example, pregnancy may increase susceptibility to toxoplasmosis and listeriosis and may increase severity of illness and increase mortality rates from influenza and varicella. 

Xenopregnancy

If the mechanisms of rejection-immunity of the fetus could be elucidated, it could avail for xenopregnancy, having, for example pigs carry human fetuses to term as an alternative to a human surrogate mother, providing a sober, drug-free and nonsmoking carrier.

(source:wikipidia)