Miscarriage

Abstract Miscarriage (the spontaneous death and expulsion of a fetus) is the most frequent problem of clinical pregnancy. It is also one of the least discussed and most erratically recorded. Studies of miscarriage rely on clinical records or self-report (both of which are incomplete) or on prospective studies, which are difficult because women must be enrolled early in pregnancy to capture all events. Most estimates of miscarriage risk among clinically recognized pregnancies are in the range of 10–15%, with sharply increasing risk as women age. A major portion of miscarried fetuses are aneuploid, with others having no apparent cause. The occurrence of miscarriage appears to be relatively stable over time and, aside from women’s age, with few known risk factors. Analytic problems include the competing risk of induced abortion, the role of selective fertility, an “unhealthy worker” effect, and reverse causation.