miscarriage

1 failure of a plan [syn: abortion]

2 a natural loss of the products of conception [syn: spontaneous abortion, stillbirth] [ant: live birth]

English

Pronunciation

• a US /ˈmɪs.kɛr.ədʒ/

Noun

1. An accidental termination of a pregnancy.
2. A spontaneous abortion.
3. A failure to properly execute a plan or achieve the expected ideals.

   The guilty verdict was a miscarriage of justice.

Translations

Miscarriage or spontaneous abortion is the natural or spontaneous end of a pregnancy at a stage where the embryo or the fetus is incapable of surviving, generally defined in humans at a gestation of prior to 20 weeks. Miscarriage is the most common complication of early pregnancy. The medical term "spontaneous abortion" is used in reference to miscarriages because the medical term "abortion" refers to any terminated pregnancy, deliberately induced or spontaneous, although in common parlance it refers specifically to active termination of pregnancy.

Terminology

Very early miscarriages - those which occur before the sixth week LMP (since the woman's Last Menstrual Period) are medically termed early pregnancy loss or chemical pregnancy. Miscarriages that occur after the sixth week LMP are medically termed clinical spontaneous abortion.

Labour resulting in live birth before the 37th week of pregnancy is termed "premature birth," even if the infant dies shortly afterward. The limit of viability at which 50% of fetus/infants survive longterm is around 24 weeks, with moderate or major neurological disability dropping to 50% only by 26 weeks. Although long-term survival has never been reported for infants born from pregnancy shorter than 21 weeks and 5 days, infants born as early as the 16th week of pregnancy may sometimes live for some minutes after birth.

A fetus that dies while in the uterus after about the 20-24th week of pregnancy is termed a "stillbirth"; the precise gestational age definition varies by country. Premature births or stillbirths are not generally considered miscarriages, though usage of the terms and causes of these events may overlap.

Forms and types

The clinical presentation of a threatened abortion describes any bleeding seen during pregnancy prior to viability, that has yet to be assessed further. At investigation it may be found that the fetus remains viable and the pregnancy continues without further problems. It has been suggested that bed rest improves the chances of the pregnancy continuing when a small subchorionic hematoma has been found on ultrasound scans.

Alternatively the following terms are used to describe pregnancies that do not continue:

• An empty sac is a condition where the gestational sac develops normally, while the embryonic part of the pregnancy is either absent or stops growing very early. Other terms for this condition are blighted ovum and anembryonic pregnancy.
• An inevitable abortion describes where the fetal heart beat is shown to have stopped and the cervix has already dilated open, but the fetus has yet to be expelled. This usually will progress to a complete abortion.
• A complete abortion is when all products of conception have been expelled. Products of conception may include the trophoblast, chorionic villi, gestational sac, yolk sac, and fetal pole (embryo); or later in pregnancy the fetus, umbilical cord, placenta, amniotic fluid, and amniotic membrane.
• An incomplete abortion occurs when tissue has been passed, but some remains in utero.
• A missed abortion is when the embryo or fetus has died, but a miscarriage has not yet occurred. It is also referred to as delayed miscarriage.

The following two terms consider wider complications or implications of a miscarriage:

• A septic abortion occurs when the tissue from a missed or incomplete abortion becomes infected. The infection of the womb carries risk of spreading infection (septicaemia) and is a grave risk to the life of the woman.
• Recurrent pregnancy loss (RPL) or recurrent miscarriage (medically termed habitual abortion) is the occurrence of three consecutive miscarriages. If the proportion of pregnancies ending in miscarriage is 15%, then the probability of two consecutive miscarriages is 2.25% and the probability of three consecutive miscarriages is 0.34%. The occurrence of recurrent pregnancy loss is 1%. A large majority (85%) of women who have had two miscarriages will conceive and carry normally afterwards.

Causes

Miscarriages can occur for many reasons, not all of which can be identified.

First trimester

Most clinically apparent miscarriages (two thirds to three-quarters in various studies) occur during the first trimester.

Chromosomal abnormalities are found in more than half of embryos miscarried in the first 13 weeks. A pregnancy with a genetic problem has a 95% chance of ending in miscarriage. Most chromosomal problems happen by chance, have nothing to do with the parents, and are unlikely to recur. Genetic problems are more likely to occur with older parents; this may account for the higher miscarriage rates observed in older women.

Another cause of early miscarriage may be progesterone deficiency. Women diagnosed with low progesterone levels in the second half of their menstrual cycle (luteal phase) may be prescribed progesterone supplements, to be taken for the first trimester of pregnancy. and even the identification of problems with the luteal phase as contributing to miscarriage has been questioned.

Second trimester

Up to 15% of pregnancy losses in the second trimester may be due to uterine malformation, growths in the uterus (fibroids), or cervical problems.

General risk factors

Pregnancies involving more than one fetus are at increased risk of miscarriage. However, a 2006 review of metformin treatment in pregnancy found insufficient evidence of safety and did not recommend routine treatment with the drug.

High blood pressure and certain illnesses (such as rubella and chlamydia) increase the risk of miscarriage. An increase in miscarriage is also associated with the father being a cigarette smoker.

Correlations

Several factors have been correlated with higher miscarriage rates, but whether they cause miscarriages is debated. No causal mechanism may be known, the studies showing a correlation may have been retrospective (beginning the study after the miscarriages occurred, which can introduce bias) rather than prospective (beginning the study before the women became pregnant), or both.

Nausea and vomiting of pregnancy (NVP, or morning sickness) are associated with a decreased risk of miscarriage. Several mechanisms have been proposed for this relationship, but none are widely agreed on. Because NVP may alter a woman's food intake and other activities during pregnancy, it may be a confounding factor when investigating possible causes of miscarriage.

One such factor is exercise. A study of over 92,000 pregnant women found that most types of exercise (with the exception of swimming) correlated with a higher risk of miscarriage prior to 18 weeks. Increasing time spent on exercise was associated with a greater risk of miscarriage: an approximately 10% increased risk was seen with up to 1.5 hours per week of exercise, and a 200% increased risk was seen with over 7 hours per week of exercise. High-impact exercise was especially associated with the increased risk. No relationship was found between exercise and miscarriage rates after the 18th week of pregnancy. The majority of miscarriages had already occurred at the time women were recruited for the study, and no information on nausea during pregnancy or exercise habits prior to pregnancy was collected.

Caffeine consumption has also been correlated to miscarriage rates, at least at higher levels of intake. A 2007 study of over 1,000 pregnant women found that women who reported consuming 200 mg or more of caffeine per day experienced a 25% miscarriage rate, compared to 13% among women who reported no caffeine consumption. 200 mg of caffeine is present in 10 oz (300 mL) of coffee or 25 oz (740 mL) of tea. This study controlled for pregnancy-associated nausea and vomiting (NVP or morning sickness): the increased miscarriage rate for heavy caffeine users was seen regardless of how NVP affected the women. About half of the miscarriages had already occurred at the time women were recruited for the study. A second 2007 study of approximately 2,400 pregnant women found that caffeine intake up to 200 mg per day was not associated with increased miscarriage rates (the study did not include women who drank more than 200 mg per day past early pregnancy).

Prevalence

Determining the prevalence of miscarriage is difficult. Many miscarriages happen very early in the pregnancy, before a woman may know she is pregnant. Treatment of women with miscarriage at home means medical statistics on miscarriage miss many cases. Prospective studies using very sensitive early pregnancy tests have found that 25% of pregnancies are miscarried by the sixth week LMP (since the woman's Last Menstrual Period). Clinical miscarriages (those occurring after the sixth week LMP) occur in 8% of pregnancies. The loss rate between 8.5 weeks LMP and birth is about two percent; loss is “virtually complete by the end of the embryonic period."

The prevalence of miscarriage increases considerably with age of the parents. One study found that pregnancies from men younger than twenty-five years are 40% less likely to end in miscarriage than pregnancies from men 25-29 years. The same study found that pregnancies from men older than forty years are 60% more likely to end in miscarriage than the 25-29 year age group. Another study found that the increased risk of miscarriage in pregnancies from older men is mainly seen in the first trimester. Yet another study found an increased risk in women, by the age of forty-five, on the order of 800% (compared to the 20-24 age group in that study), 75% of pregnancies ended in miscarriage.

Detection

The most common symptom of a miscarriage is bleeding; bleeding during pregnancy may be referred to as a threatened abortion. Of women who seek clinical treatment for bleeding during pregnancy, about half will go on to have a miscarriage.

If the bleeding is light, making an appointment to see one's doctor is recommended. If bleeding is heavy, there is considerable pain, or there is a fever, then emergency medical attention is recommended to be sought.

No treatment is necessary for a diagnosis of complete abortion (as long as ectopic pregnancy is ruled out). In cases of an incomplete abortion, empty sac, or missed abortion there are three treatment options:

• With no treatment (watchful waiting), most of these cases (65-80%) will pass naturally within two to six weeks. This path avoids the side effects and complications possible from medications and surgery.
• Medical management usually consists of using misoprostol (a prostaglandin, brand name Cytotec) to encourage completion of the miscarriage. About 95% of cases treated with misoprostol will complete within a few days.

ICD10 codes

Notes

See also

• Childbirth
• Stillbirth
• Sudden antenatal death syndrome
• Premature birth

External links

• Spontaneous Abortion
• Hormones predict miscarriage risk
• Miscarriage Overview
• Frequently asked questions about recurrent miscarriage/recurrent pregnancy loss

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