Definition of Miscarriage:

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

Causes, incidence, and risk factors:

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