Maternal smoking, pregnancy complications, and perinatal mortality.

Analysis of data from the Ontario Perinatal Mortality Study has shown that perinatal mortality increases directly with the level of maternal smoking during pregnancy. Increases in smoking level are associated with increases in the frequency of early fetal deaths and of neonatal deaths due to premature delivery. These deaths in turn are associated with smoking-related increases in the incidence of bleeding during pregnancy, abruptio placentae, placenta previa, and premature and prolonged rupture of the membranes.