Miscarriage
(Spontaneous Abortion)

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR

• What is a miscarriage?
• What causes a miscarriage, and what are the tests for the different causes?
• What does NOT cause miscarriage?
• Are there lifestyle factors associated with miscarriage?
• What are the symptoms of a miscarriage?
• What will the doctor look for during an examination with suspected miscarriage?
• How is threatened abortion evaluated?
• What are common terms a woman might hear during evaluation for miscarriage?
• What treatment can a woman expect when she has had a miscarriage?
• When should a woman receive evaluation for underlying causes of pregnancy loss?
• Can something be done to prevent future miscarriages?
• Miscarriage At A Glance

What is a miscarriage?

A miscarriage (spontaneous abortion) is any pregnancy that ends spontaneously before the fetus can survive. The World Health Organization defines this unsurvivable state as an embryo or fetus weighing 500 grams or less, which typically corresponds to a fetal age (gestational age) of 20 to 22 weeks or less. Miscarriage occurs in about 15-20% of all recognized pregnancies, and usually occurs before the 13th week of pregnancy. The actual percentage of miscarriages is estimated to be as high as 50% of all pregnancies, since many miscarriages occur without the woman ever having known she was pregnant. Of those miscarriages that occur before the eighth week, 30% have no fetus associated with the sac or placenta. This condition is called blighted ovum, and many women are surprised to learn that there was never an embryo inside the sac.

Some miscarriages occur before women recognize that they are pregnant. About 15% of fertilized eggs are lost before the egg even has a chance to implant (embed itself) in the wall of the uterus. A woman would not generally identify this type of miscarriage. Another 15% of conceptions are lost before eight weeks' gestation. Once fetal heart function is detected in a given pregnancy, the chance of miscarriage is less than 5%.

A woman who may be showing the signs of a possible miscarriage (such as vaginal bleeding) may hear the term "threatened abortion" used to describe her situation.

Next: What causes a miscarriage, and what are the tests for the different causes? »