A miscarriage (spontaneous abortion) is the loss of a fetus due to natural causes before 20 weeks of pregnancy.
A miscarriage occurs in about 10 to 15% of recognized pregnancies. Many more miscarriages are unrecognized because they occur before women know they are pregnant. About 85% of miscarriages occur during the first 12 weeks of pregnancy, and as many as 25% of all pregnancies end in a miscarriage during the first 12 weeks of pregnancy. Miscarriages are more common in high-risk pregnancies, particularly when women are not receiving adequate medical care (see High-Risk Pregnancy).
Most miscarriages that occur during the first 12 weeks of pregnancy are thought to occur because something was wrong with the fetus, such as a birth defect or a genetic disorder.
If women have a disorder that causes blood to clot too easily (such as antiphospholipid antibody syndrome), they may have repeated miscarriages that occur after 10 weeks of pregnancy.
The remaining 15% of miscarriages occur during weeks 13 to 20. For many of these miscarriages, no cause is identified. The rest result from problems in the woman, such as the following:
Rh incompatibility (when a pregnant woman has Rh-negative blood and the fetus has Rh-positive blood) also increases risk of miscarriage. Sudden emotional shock (for example, resulting from receiving bad news) and minor injuries (for example, resulting from slipping and falling) are not linked with miscarriage.
A miscarriage is more likely if women have had a miscarriage or preterm labor in a previous pregnancy. For women who have had two or more consecutive miscarriages, the chance of having another miscarriage is about
The more miscarriages a woman has had, the higher the risk of having another miscarriage. The risk of having another miscarriage also depends on what the cause is. Some causes, if not corrected or treated, tend to cause repeated miscarriages. When women have had several miscarriages, the cause may be an abnormality in their or the father's chromosomes or antiphospholipid antibody syndrome.
A miscarriage is usually preceded by spotting with bright or dark red blood or more obvious bleeding. The uterus contracts, causing cramps. However, about 20 to 30% of pregnant women have some bleeding at least once during the first 20 weeks of pregnancy. About half of these episodes result in a miscarriage.
Early in a pregnancy, the only sign of a miscarriage may be a small amount of vaginal bleeding. Later in a pregnancy, a miscarriage may cause profuse bleeding, and the blood may contain mucus or clots. Cramps become more severe until eventually, the uterus contracts enough to expel the fetus and placenta.
Sometimes the fetus dies but no symptoms of miscarriage occur. In such cases, the uterus does not enlarge. Rarely, the dead tissues in the uterus become infected before, during, or after a miscarriage. Such an infection (called a septic abortion) may be serious, causing fever, chills, and a rapid heart rate. Affected women may become delirious, and blood pressure may become dangerously low.
If a pregnant woman has bleeding and cramping during the first 20 weeks of pregnancy, a doctor examines her to determine whether a miscarriage is likely. The doctor examines the cervix to determine whether it is dilating or pulling back (effacing). If it is not, the pregnancy may be able to continue. If it is dilating or effacing, a miscarriage is very likely.
Ultrasonography is usually also done. It may be used to determine whether a miscarriage has already occurred or, if not, whether the fetus is still alive. If a miscarriage has occurred, ultrasonography can show whether the fetus and the placenta have been expelled.
Usually, doctors do blood tests to measure a hormone produced by the placenta early in pregnancy called human chorionic gonadotropin (hCG). Results enable doctors to determine whether a woman has a mislocated (ectopic) pregnancy, which can also cause bleeding. This test can also help doctors determine whether parts of the fetus or placenta remain in the uterus after a miscarriage.
If women have had several miscarriages, they may want to see a doctor before they try to become pregnant again. The doctor can check for genetic or structural abnormalities and for other disorders that increase the risk of a miscarriage. For example, an imaging test (such as ultrasonography, hysteroscopy, or hysterosalpingography) may be done to look for structural abnormalities, blood tests can be done to check for antiphospholipid antibody syndrome, and genetic tests may be done to check for chromosomal abnormalities. If identified, some causes of a previous miscarriage can be treated, making a successful pregnancy possible.
If the fetus is alive, some doctors advise women to avoid strenuous activity and, if possible, to stay off their feet. However, there is no clear evidence that such limitations are helpful. There is also no evidence that refraining from sexual intercourse helps. Miscarriage cannot be prevented.
If a miscarriage has occurred and the fetus and the placenta have been completely expelled, no treatment is needed.
If some tissue from the fetus or placenta remains in the uterus after a miscarriage or if the fetus dies and remains in the uterus, doctors may do one of the following:
Before surgically removing the fetus, doctors may use natural substances that absorb fluids (such as seaweed stems) to help open the cervix. Or they may give the woman a prostaglandin (a hormonelike drug that stimulates the uterus to contract), such as misoprostol. These treatments make removal of the tissues easier.
If a drug is used, suction curettage or D & E may be needed afterward to remove pieces of the placenta. D & E may not be available because it requires special training.
If women have symptoms of a septic abortion, the contents of the uterus are removed as soon as possible, and women are treated with antibiotics, given intravenously.
Emotions after miscarriage:
After a miscarriage, women may feel grief, sadness, anger, guilt, or anxiety about subsequent pregnancies.
Last full review/revision August 2013 by Antonette T. Dulay, MD