Epidemiology of hydatidiform mole during early gestation.

Different methodologic approaches have resulted in a wide variability in the reported incidence of hydatidiform mole in the United States. We studied the epidemiology of hydatidiform mole among 84,318 women obtaining legal abortions in the United States during the period 1975 to 1978. Our estimated rate of 7.5 hydatidiform moles per 10,000 pregnancies was similar to most reported rates for the United States. The rate was significantly higher for women 14 years or younger and those 45 years or older. Race, number of previous pregnancies, and number of previous spontaneous abortions were not found to significantly affect the risk of having the disease. The incidence was slightly (but not significantly) higher for women obtaining abortions during the first trimester than for those obtaining abortions during later gestation. This study minimizes the errors encountered in estimating the total number of pregnancies and the number of hydatidiform moles at later stages of gestation. Hydatidiform mole, although relatively the number of hydatidiform moles at later stages of gestation. Hydatidiform mole, although relatively uncommon, represents a complication of pregnancy that is of public health importance.