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(Spontaneous Abortion)


Antonette T. Dulay

, MD, Main Line Health System

Last full review/revision Oct 2020| Content last modified Sep 2022
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A miscarriage 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 a structural abnormality of the reproductive organs, infection, 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.

Pregnancy complications are problems that occur only during pregnancy. They may affect the woman, the fetus, or both and may occur at different times during the pregnancy. However, most pregnancy complications can be effectively treated. Miscarriage, by definition, involves death of the fetus, and it may increase the risk of miscarriage in future pregnancies.

A miscarriage occurs in up 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. The remaining 15% of miscarriages occur during weeks 13 to 20.

Miscarriages are more common in high-risk pregnancies High-Risk Pregnancy , particularly when women are not receiving adequate medical care.

Causes of Miscarriage

Most miscarriages that occur during the first 10 to 11 weeks of pregnancy are thought to occur because of a genetic disorder. Sometimes miscarriages result from a birth defect.

If women have a disorder that causes blood to clot too easily (such as antiphospholipid antibody syndrome Antiphospholipid Syndrome Autoimmune disorders, including Graves disease, are more common among women, particularly pregnant women. The abnormal antibodies produced in autoimmune disorders can cross the placenta and... read more ), they may have repeated miscarriages (called recurrent pregnancy loss) that occur after 10 weeks of pregnancy.

For many of the miscarriages that occur during weeks 13 to 20, no cause is identified.

Risk factors (conditions that increase the risk of a disorder) for miscarriage include the following:

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 in a previous pregnancy.

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, but overall, women who have had several miscarriages have about a 1 in 4 chance of having a miscarriage in a later pregnancy.

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.

Understanding the Language of Loss

Doctors may use the term abortion to refer to a miscarriage (spontaneous abortion), as well as to intentional termination of pregnancy for medical or other reasons (induced abortion). After 20 weeks of pregnancy, delivery of a fetus that has died is called a stillbirth.

Other terms for abortion include the following:

  • Therapeutic (induced) abortion: An abortion that is brought about by medical means (drugs or surgery)—for example, because the woman’s life or health is endangered or the fetus has major abnormalities

  • Threatened abortion: Bleeding or cramping during the first 20 weeks of pregnancy without opening (dilation) of the cervix, indicating that the fetus may be lost

  • Inevitable abortion: Pain or bleeding during first 20 weeks of pregnancy with dilation of the cervix, indicating that the fetus will be lost

  • Complete abortion: Expulsion of all of the fetus and placenta in the uterus

  • Incomplete abortion: Expulsion of only part of the contents of the uterus

  • Missed abortion: Retention of a dead fetus in the uterus

  • Septic abortion: Infection of the contents of the uterus before, during, or after an abortion

Symptoms of Miscarriage

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% 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 infections (called a septic abortion) usually result from induced abortions done by untrained practitioners who do not use sterile techniques. Septic abortion may be serious, causing fever, chills, bleeding, and a rapid heart rate. Affected women may become delirious, and blood pressure may become dangerously low.

Did You Know...

  • Many miscarriages are unrecognized because they occur before women know they are pregnant.

  • About 20% of pregnant women have some bleeding at least once during the first 20 weeks of pregnancy, and about half of these women have a miscarriage.

Diagnosis of Miscarriage

  • A doctor's evaluation

  • Ultrasonography

  • Blood tests

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 before 20 weeks of pregnancy, a miscarriage is highly 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 Ectopic Pregnancy Ectopic pregnancy is attachment (implantation) of a fertilized egg in an abnormal location. In an ectopic pregnancy, the fetus cannot survive. When an ectopic pregnancy ruptures, women often... read more , 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.

Doctors can usually diagnose septic abortion based on the woman's circumstances and symptoms. If septic abortion seems likely, doctors send a sample of blood to a laboratory to be cultured (placed in substance that encourages microorganisms to grow). This technique helps doctors identify the microorganism causing the infection and thus determine which antibiotics would be effective.

If women have had several miscarriages, they may want to see a doctor before they try to become pregnant again. The doctor can check them for genetic or structural abnormalities and for other disorders that increase the risk of a miscarriage. For example, doctors may do the following:

  • An imaging test (such as ultrasonography, hysteroscopy, or hysterosalpingography) to look for structural abnormalities

  • Blood tests to check for certain disorders, such as antiphospholipid antibody syndrome, diabetes, hormone abnormalities, and thyroid disorders

  • Genetic tests to check for chromosomal abnormalities

If identified, some causes of a previous miscarriage can be treated, making a successful pregnancy possible.

Treatment of Miscarriage

  • For threatened abortion, periodic evaluation of the woman's symptoms

  • For complete abortion, no treatment

  • For other types of abortion, removal of the contents of the uterus

  • Emotional support

If the fetus is alive and the cervix has not opened (threatened abortion), no specific treatment can help, but doctors periodically evaluate the woman's symptoms or do ultrasonography.

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.

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 during the 1st or 2nd trimester, 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.

  • 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.

Doctors offer their support and, when appropriate, reassure women that the miscarriage was not their fault. Formal counseling is rarely needed, but doctors make it available for women who want it.

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