We know that smoking can cause ectopic pregnancies, miscarriages, premature rupture of the membranes, placenta previa (an unusual low position), and placental abruption (a breaking away from the wall of the uterus). Smoking can also cause premature delivery.
U.S. Department of Health and Human Services. The Health Consequences of Smoking – 50 years of Progress: A Report of the Surgeon General. Atlanta, GA. Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2014.