Marihuana and tobacco smoking are two of the most commonly abused subs
tances in pregnancy. Smoke from both agents contain a multitude of pot
entially active components, which make them difficult to study. Both h
ave been associated with adverse effects in pregnancy in animal and hu
man studies. Data on marihuana use during pregnancy have been conflict
ing. There is much evidence, however, demonstrating adverse pregnancy
outcomes associated with cigarette smoking which, fortunately, can be
reversed with smoking cessation.