Approximately 20% of pregnant women experience some vaginal bleeding, with or without abdominal cramping, during the first trimester. This is known as a threatened abortion. However, most of these pregnancies go on to term with or without treatment. Spontaneous abortion occurs in less than 30% of the women who experience vaginal bleeding during pregnancy.

In the cases that result in spontaneous abortion, the usual cause is fetal death. Such death is typically the result of a chromosomal or developmental abnormality. Other potential causes include infection, maternal anatomic defects, endocrine factors, immunologic factors, and maternal systemic disease.

Estimates report that up to 50% of all fertilized eggs abort spontaneously, usually before the woman knows she is pregnant. Among known pregnancies, the rate is approximately 10%. These usually occur between 7 and 12 weeks of gestation. Increased risk is associated with women over age 35, women with systemic disease (such as diabetes or thyroid dysfunction), and those with a history of 3 or more prior spontaneous abortions.

• Vaginal bleeding during the first 20 weeks of pregnancy (last menstrual period was less than 20 weeks ago)
• Abdominal cramps may or may not accompany vaginal bleeding

Note: With true miscarriage, low back pain or abdominal pain (dull to sharp, constant to intermittent) typically occurs and tissue or clot-like material may pass from the vagina.

Pelvic examination reveals a cervix that is neither thinned (effaced) nor open (dilated). The presence of effacement and/or dilation is consistent with impending miscarriage.

• A serum HCG may be performed to confirm that a pregnancy exists.
• Beta HCG (quantitative) test may be repeated over a period of days or weeks to confirm either continued pregnancy or fetal death.
• A CBC may be obtained to determine the degree of blood loss.
• A WBC with differential may be obtained to rule out infection.
• A pregnancy ultrasound is used to detect fetal heartbeat.

This disease may also alter the results of the following tests:

• Serum progesterone
• Beta HCG (quantitative)

Activity restrictions vary, from avoiding some forms of exercise to complete bed rest. Restricting activity will not guarantee that a miscarriage will not occur. Providers typically recommend pelvic rest (abstaining from intercourse, douching, tampon use) until symptoms resolve. The woman's condition should be monitored carefully.

The use of progesterone is controversial. The potential benefit is the relaxation of smooth muscle, including the muscles of the uterus. However, this may increase the potential risk of an incomplete abortion or an abnormal pregnancy. It also increases the risk of retaining a hydatidiform mole. In the absence of a luteal phase defect, progesterone supplementation should not be used.

The probable outcome is good when the pregnancy continues to progress and all the symptoms disappear.

• Spontaneous abortion
• Moderate to heavy blood loss
• Anemia
• Dead fetus syndrome
• Infection

It is imperative for a woman who knows she is (or is likely to be) pregnant and who has any signs or symptoms of threatened abortion to contact her prenatal provider immediately.

Early and comprehensive prenatal care decreases risk. It is preferable to detect and treat known maternal disorders before conception occurs. Avoiding environmental hazards such as X-rays and infectious diseases also decreases the risk of miscarriage in early pregnancy.

Spontaneous abortion is not preventable if there is fetal death. In fact, it is important for the uterus to expel all products of conception in such cases. A missed abortion occurs when a dead fetus is not expelled from the uterus. When only part of the dead fetus is expelled, it is an incomplete abortion.