Association of induced abortion with subsequent pregnancy loss.

We compared prior pregnancy histories of two groups of multigravidas--240 women having a pregnancy loss up to 28 weeks' gestation and 1,072 women having a term delivery. Women who had had two or more prior induced abortions had a twofold to threefold increase in risk of first-trimester spontaneous abortion, loss between 14 to 19 and 20 to 27 weeks. The increased risk was present for women who had legal induced abortions since 1973. It was not explained by smoking status, history of prior spontaneous loss, prior abortion method, or degree of cervical dilatation. No increase in risk of pregnancy loss was detected among women with a single prior induced abortion. We conclude that multiple induced abortions do increase the risk of subsequent pregnancy losses up to 28 weeks' gestation.