Coitus late in pregnancy has been thought to be a cause of premature rupture of membranes, preterm birth, and amniotic fluid infections. In this study, data on 10 981 singleton, low-risk pregnancies were examined. The mothers were asked at time of delivery if there were any months when they did not have sexual intercourse during pregnancy. Pregnancy outcomes were determined by medical record review. Those having intercourse showed no increased risk of premature rupture of membranes, low birthweight, or perinatal death at any gestational age. Women abstaining from intercourse had more unfavourable outcomes in the seventh and eighth months, but these differences were almost eliminated by adjustment for maternal age. Preterm delivery was no more frequent in those having intercourse than in those abstaining. These findings challenge the view that intercourse late in pregnancy is harmful.