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.