Merck Manual

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(Spontaneous Abortion; Pregnancy Loss)


Antonette T. Dulay

, MD, Main Line Health System

Reviewed/Revised Oct 2022
Topic Resources

A miscarriage is the loss of a fetus 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 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. 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

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.

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 (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:

  • Early: Loss of the fetus before 12 weeks of pregnancy

  • Late: Loss of the fetus between 12 and 20 weeks of pregnancy

  • 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

  • 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: Closed cervix after expulsion of all of the fetus and placenta in the uterus

  • Incomplete abortion: Dilation of the cervix and expulsion of only part of the contents of the uterus

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

  • Recurrent abortion: At least two miscarriages

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

  • Spontaneous abortion: Loss of the fetus before 20 weeks of pregnancy

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 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. If any fragments of the fetus or placenta remain in the uterus, infection may develop.

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. Infection of the uterus that occurs during or shortly before or after a miscarriage or an abortion is called a septic abortion Septic Abortion Septic abortion is a serious infection of the uterus that occurs shortly before, during, or shortly after an abortion or a miscarriage. Septic abortions usually develop when untrained practitioners... read more .

Did You Know...

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

  • About 20 to 30% 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. A pelvic examination Pelvic Examination For gynecologic care, a woman should choose a health care practitioner with whom she can comfortably discuss sensitive topics, such as sex, birth control, pregnancy, and problems related to... read more is done. 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 completely 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, such as the fallopian tubes. In an ectopic pregnancy, the fetus cannot survive. When an ectopic pregnancy... read more , which can also cause bleeding. This test can also help doctors determine whether the fetus is alive, whether a miscarriage has occurred, and, if so, whether parts of the fetus or placenta remain in the uterus after the miscarriage.

If the uterus does not progressively enlarge or if hCG levels do not increase as expected during pregnancy, doctors suspect a missed abortion. That is, the fetus has died but has not been expelled from the uterus.

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 chromosome abnormalities

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

Treatment of Miscarriage

  • For complete abortion, no treatment

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

  • For inevitable, incomplete, or missed abortions, observation or removal of the contents of the uterus

  • Rho(D) immune globulin if the mother has Rh-negative blood

  • Sometimes pain relievers

  • Emotional support

If a miscarriage has occurred and the fetus and the placenta have been completely expelled, no treatment is needed.

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 activity helps.

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 hormone-like 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.

Pain relievers are given as needed.

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. Support groups may be helpful.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Korlym, Mifeprex
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