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Abortion - threatened

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Definition:

A threatened abortion is a condition of pregnancy, occurring before the 20th week of gestation, that suggests potential miscarriage may take place.

Alternative Names:

Threatened miscarriage; Threatened spontaneous abortion

Causes, incidence, and risk factors:

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.

• Review Date: 8/8/2005
• Reviewed By: Sharon Roseanne Thompson, M.D., M.P.H., Clinical Fellow, Department of Obstetrics & Gynecology, Brigham and Women's Hospital, Boston, MA. Review provided by VeriMed Healthcare Network.

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