A miscarriage is the spontaneous loss of a fetus before the 20th week of pregnancy. (Pregnancy losses after the 20th week are called preterm deliveries.)

A miscarriage may also be called a "spontaneous abortion." This refers to naturally occurring events, not elective or therapeutic abortion procedures, which a woman may choose to have done.

Other terms for the early loss of pregnancy include:

• Missed abortion (a loss of pregnancy where the products of conception do not exit the body)
• Incomplete abortion (not all of the products of conception exit the body)
• Complete abortion (all of the products of conception exit the body)
• Threatened abortion (symptoms indicate a miscarriage is possible)
• Inevitable abortion (the symptoms cannot be stopped, and a miscarriage will happen)
• Infected abortion

Most miscarriages occur when the unborn baby has deadly genetic problems. Usually, these problems are unrelated to the mother.

Other possible causes for miscarriage include:

• Infection
• Physical problems in the mother
• Hormonal factors
• Immune responses
• Serious systemic diseases of the mother (such as diabetes or thyroid disease)

It is estimated that up to 50% of all fertilized eggs die and are lost (aborted) spontaneously, usually before the woman knows she is pregnant. Among known pregnancies, the rate of miscarriage is approximately 10% and usually occurs between the 7th and 12th weeks of pregnancy.

The risk for miscarriage is higher in women:

• Over age 35
• With certain diseases such as diabetes or thyroid problems
• With a history of three or more prior miscarriages

Possible symptoms include:

• Low back pain or abdominal pain that is dull, sharp, or cramping
• Vaginal bleeding, with or without abdominal cramps
• Tissue or clot-like material that passes from the vagina

However, about 20% of pregnant women have some vaginal bleeding during the first 3 months of pregnancy. Approximately half of these women have a miscarriage.

During a pelvic exam, your health care provider may see moderate thinning of your cervix (effacement), increased cervical dilation, and evidence of ruptured membranes.

The following tests may be performed:

• HCG (qualitative) to confirm pregnancy
• HCG (quantitative) done every several days or weeks
• CBC to determine how much blood has been lost
• WBC and differential to rule out infection
• Blood type (if you have an Rh- blood type, you would require a treatment with Rh-immune globulin. See: Rh incompatibility)

If there is threat of miscarriage, you may be told to avoid or restrict some forms of exercise or you may need complete bed rest. Not having sexual intercourse is usually recommended until the warning signs have disappeared.

If a miscarriage occurs, the tissue passed from the vagina should be examined to determine if it was a fetus or a hydatidiform mole. It is also important to determine whether any fetal tissue remains in the uterus. This is called an incomplete spontaneous abortion.

If remaining tissue does not naturally exit the body, he woman may be closely watched for up to 2 weeks. Surgery (D and C) or medication (such as misoprostol) may be needed to help the uterus eliminate the remaining contents. Most women who use these medications do so because of a desire to avoid anesthesia and surgery.

Side effects of the medication may include nausea, vomiting, diarrhea, warmth or chills, headache, more visits to the doctor’s office, prolonged vaginal bleeding, and being more aware of cramping than with surgical abortion. With medication, passage of the products of pregnancy most likely will occur at home, but some women may still require a surgical procedure (D and C) to complete remove all products of the pregnancy.

After treatment, the woman usually resumes her normal menstrual cycle within a few weeks. Any further vaginal bleeding should be carefully monitored. It is often possible to become pregnant immediately; however, it is recommended that women wait for one normal menstrual cycle before trying to become pregnant again.

Complications in the mother are rare. However, possible complications include infection, which may need to be surgically treated.

Women who lose a baby during the second or third trimester of pregnancy receive different medical care. If the dead fetus remains in the uterus for too long, blood clotting can develop. This can threaten the mother's health.

Call your health care provider if vaginal bleeding with or without cramping occurs during pregnancy.

Call your health care provider if you are pregnant and notice tissue or clot-like material passed vaginally (any such material should be collected and brought in for examination).

Many miscarriages that are caused by systemic diseases can be prevented by detecting and treating the disease before becoming pregnant.

Miscarriages are less likely if you receive early, comprehensive prenatal care and avoid environmental hazards (such as x-rays and infectious diseases).

When a mother's body is having difficulty sustaining a pregnancy, signs (such as slight vaginal bleeding) may occur. This is a threatened abortion, which means there is a possibility of miscarriage, but it does not mean one will definitely occur. A pregnant woman who develops any signs or symptoms of threatened miscarriage should contact her prenatal provider immediately.