Pregnancy loss is the unexpected loss of a fetus before the 20th week of pregnancy. It is sometimes called miscarriage, early pregnancy loss, mid-trimester pregnancy loss, fetal demise, or spontaneous abortion.
Health care providers use a different term—stillbirth—to describe the loss of a fetus after 20 weeks of pregnancy.
Pregnancy loss may occur so early that a woman may not know she was pregnant.1
Researchers can only estimate the number of women who experience pregnancy loss, because some losses occur before a woman's pregnancy is confirmed by a health care provider or pregnancy test. But the American College of Obstetricians and Gynecologists estimates that early pregnancy loss is common, occurring in about 10% of confirmed pregnancies.2