Abortion, spontaneous

Alternative names:

miscarriage

Definition:

The loss of a fetus during pregnancy due to natural causes (usually due to fetal death). A miscarriage; the spontaneous termination of a pregnancy before fetal development adequate for survival (usually about 20 weeks). A natural event, not an elective or therapeutic abortion procedure. See also: incomplete abortion (not all of the products of conception are expelled); complete abortion (all of the products of conception are expelled); threatened abortion (symptoms indicate a miscarriage is possible); inevitable abortion (the symptoms cannot be stopped, a miscarriage will happen); infected abortion

Causes, incidence, and risk factors:

The cause of most spontaneous abortions is fetal death due to fetal growth abnormalities, not caused by the mother. Other possible causes for spontaneous abortion include: infection, physical defects of the mother, hormone (endocrine) factors, immune responses, and serious systemic diseases of the mother (such as diabetes or thyroid problems).

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 spontaneous abortion is approximately 10% and usually occurs between the 7th and 12th weeks of pregnancy (gestation).

The risk for spontaneous abortion is increased in women over 35 years of age, women with systemic disease (such as diabetes or thyroid dysfunction) and those with a history of 3 or more prior spontaneous abortions.