Carbon monoxide and nicotine in cigarettes cause hypoxia and vasoconstriction, increasing risk of the following: Spontaneous abortion (fetal loss or delivery < 20 weeks) Fetal growth restriction Abruptio placentae (placental abruption) Placenta previa Premature rupture of the membranes Preterm birth Intra-amniotic infection Stillbirth Neonates whose mothers smoke are also more likely to have anencephaly, congenital heart defects, orofacial clefts, sudden infant death syndrome, deficiencies in physical growth and intelligence, and behavioral problems.