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A miscarriage (spontaneous abortion) is the loss of a fetus due to natural causes before 20 weeks of pregnancy.
Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect) or in the woman (such as structural abnormalities of the reproductive organs, chromosomal abnormalities, infections, use of cocaine or alcohol, cigarette smoking, or an injury), but the cause is often unknown.
Bleeding and cramping may occur, particularly late in the pregnancy.
Doctors examine the cervix and usually do ultrasonography.
If any remnants of the pregnancy remain in the uterus after a miscarriage, they are removed.
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:
Structural abnormalities of the reproductive organs, such as fibroids, scar tissue, a double uterus, or an incompetent cervix, which tends to open (dilate) as the uterus enlarges
Use of substances such as cocaine, alcohol, and tobacco (via cigarette smoking)
Infections such as a cytomegalovirus infection or rubella
An underactive thyroid gland (hypothyroidism) if the condition is severe or poorly controlled
Diabetes if it is severe or poorly controlled
Certain disorders, such as celiac disease, chronic kidney disease, systemic lupus erythematosus (lupus), and high blood pressure, if they are not appropriately treated and controlled during pregnancy
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:
If women have no fever and do not appear ill, closely monitor them while waiting to see whether the uterus will expel its contents on its own
Surgically remove the fetus and placenta through the vagina (using suction curettage or dilation and evacuation [D & E]—see Surgical evacuation), usually during the first 23 weeks of pregnancy
Use a drug that can induce labor and thus expel the contents of the uterus, such as oxytocin (usually used later in the pregnancy) or misoprostol (usually used earlier in the pregnancy)
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.
After a miscarriage, women may feel grief, sadness, anger, guilt, or anxiety about subsequent pregnancies.
Grief: Grief for a loss is a natural response and should not be suppressed or denied. Talking about their feelings with another person may help women deal with their feelings and gain perspective.
Guilt: Women may think that they did something to cause the miscarriage. Usually, they have not. Women may recall taking a common over-the-counter drug early in pregnancy, drinking a glass of wine before they knew they were pregnant, or doing another everyday thing. These things are almost never the cause of a miscarriage, so women should not feel guilty about them.
Anxiety: Women who have had a miscarriage may wish to talk with their doctor about the likelihood of a miscarriage in subsequent pregnancies and be tested if needed. Although having a miscarriage increases the risk of having another one, most of these women can become pregnant again and carry a healthy baby to term.
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