A miscarriage is the spontaneous loss of a fetus before the 20th week of pregnancy. (Pregnancy losses after the 20th week are called stillbirths.)
A miscarriage may also be called a "spontaneous abortion." This refers to naturally occurring events, not to medical abortions or surgical abortions.
Other terms for the early loss of pregnancy include:
- Complete abortion: All of the products (tissue) of conception leave the body.
- Incomplete abortion: Only some of the products of conception leave the body.
- Inevitable abortion: Symptoms cannot be stopped and a miscarriage will happen.
- Infected (septic) abortion: The lining of the womb (uterus) and any remaining products of conception become infected.
- Missed abortion: The pregnancy is lost and the products of conception do not leave the body.
Your health care provider may also use the term "threatened miscarriage." The symptoms of this condition are abdominal cramps with or without vaginal bleeding. They are a sign that a miscarriage may occur.
Abortion - spontaneous; Spontaneous abortion; Abortion - missed; Abortion - incomplete; Abortion - complete; Abortion - inevitable; Abortion - infected; Missed abortion; Incomplete abortion; Complete abortion; Inevitable abortion; Infected abortion
Most miscarriages are caused by chromosome problems that make it impossible for the baby to develop. Usually, these problems are not related to the mother's or father's genes.
Other possible causes of miscarriage include:
- Drug and alcohol abuse
- Exposure to environmental toxins
- Hormone problems
- Physical problems with the mother's reproductive organs
- Problem with the body's immune response
- Serious body-wide (systemic) diseases in the mother (such as uncontrolled diabetes)
Around half of all fertilized eggs die and are lost (aborted) spontaneously, usually before the woman knows she is pregnant. Among women who know they are pregnant, 15 to 20 out of every 100 will have a miscarriage. Most miscarriages occur during the first 7 weeks of pregnancy. The rate of miscarriage drops after the baby's heartbeat is detected.
The risk of miscarriage is higher in women:
- Who are older. The risk increases after age 30, becomes even greater between 35 and 40, and is highest after 40.
- Who have had previous miscarriages.