Miscarriage is the loss of a pregnancy in the first 20 weeks. About 15 to 20 percent of known pregnancies end in miscarriage, and more than 80 percent of these losses happen before 12 weeks.
This doesn't include situations in which you lose a fertilized egg before you get a positive pregnancy test. Studies have found that 30 to 50 percent of fertilized eggs are lost before a woman finds out she's pregnant, because they're lost so early that she goes on to get her period about on time -- in other words the woman doesn't realize she was pregnant at all.
If you lose a baby after 20 weeks of pregnancy, it's called a stillbirth.
