The epidemiology of smoking during pregnancy: smoking prevalence, maternal characteristics, and pregnancy outcomes Sven Cnattingius Smoking during pregnancy varies widely across countries. In many industrialized countries, smoking rates have peaked and begun to decline, while in others, smoking among young women is increasing. Randomized controlled trials have shown limited success in smoking interventions during pregnancy. Smoking is the most important preventable risk factor for adverse pregnancy outcomes, causing fetal growth restriction, stillbirth, preterm birth, placental abruption, and possibly sudden infant death syndrome. Smoking during pregnancy is also associated with increased risks of spontaneous abortions, ectopic pregnancies, placenta previa, and behavioral disorders in children. Smoking prevalence among women has decreased in most ethnic groups since 1965, with the largest declines among highly educated women. Smoking prevalence among young women has declined, but the reduction has leveled off in recent years. In the United States, smoking prevalence among pregnant women has decreased from 40% in 1967 to 12% in 2000. In Sweden, smoking prevalence among pregnant women has declined rapidly, from 31% in 1983 to 13% in 2000. In Denmark, smoking prevalence among pregnant women has also declined significantly. Smoking cessation among pregnant women is often due to concerns about fetal and infant health. Observation studies suggest that 20%–40% of smokers quit during pregnancy. Most women who stop smoking do so in early pregnancy. Smoking cessation is more common among women with higher education levels and among non-Hispanic Whites, Native Americans, and Alaskan natives. Smoking during pregnancy is associated with increased risks of adverse pregnancy outcomes, including spontaneous abortion, ectopic pregnancy, placental complications, fetal growth restriction, preterm birth, stillbirth, and neonatal mortality. Smoking is also associated with increased risks of congenital malformations, such as oral-facial clefts. Smoking during pregnancy is consistently associated with an increased risk of sudden infant death syndrome (SIDS), with the risk being doubled or tripled in infants of daily smokers compared to nonsmokers. Smoking during pregnancy is also associated with increased risks of hospitalization and respiratory disorders in infancy and childhood. Maternal smoking during pregnancy is associated with increased risks of lower respiratory illnesses and childhood asthma. Smoking during pregnancy is also associated with increased risks of behavioral and psychiatric disorders in childhood. Smoking during pregnancy is associated with increased risks of perinatal mortality, including stillbirth and early neonatal mortality. Smoking is also associated with increased risks of placental abruption, placenta previa, and preterm birth. Smoking during pregnancy is associated with increased risks of gestational hypertension and preeclampsia, which are leading causes of maternal mortality in the United States. Smoking during pregnancy is associated with increased risks of congenital malformations, including oralThe epidemiology of smoking during pregnancy: smoking prevalence, maternal characteristics, and pregnancy outcomes Sven Cnattingius Smoking during pregnancy varies widely across countries. In many industrialized countries, smoking rates have peaked and begun to decline, while in others, smoking among young women is increasing. Randomized controlled trials have shown limited success in smoking interventions during pregnancy. Smoking is the most important preventable risk factor for adverse pregnancy outcomes, causing fetal growth restriction, stillbirth, preterm birth, placental abruption, and possibly sudden infant death syndrome. Smoking during pregnancy is also associated with increased risks of spontaneous abortions, ectopic pregnancies, placenta previa, and behavioral disorders in children. Smoking prevalence among women has decreased in most ethnic groups since 1965, with the largest declines among highly educated women. Smoking prevalence among young women has declined, but the reduction has leveled off in recent years. In the United States, smoking prevalence among pregnant women has decreased from 40% in 1967 to 12% in 2000. In Sweden, smoking prevalence among pregnant women has declined rapidly, from 31% in 1983 to 13% in 2000. In Denmark, smoking prevalence among pregnant women has also declined significantly. Smoking cessation among pregnant women is often due to concerns about fetal and infant health. Observation studies suggest that 20%–40% of smokers quit during pregnancy. Most women who stop smoking do so in early pregnancy. Smoking cessation is more common among women with higher education levels and among non-Hispanic Whites, Native Americans, and Alaskan natives. Smoking during pregnancy is associated with increased risks of adverse pregnancy outcomes, including spontaneous abortion, ectopic pregnancy, placental complications, fetal growth restriction, preterm birth, stillbirth, and neonatal mortality. Smoking is also associated with increased risks of congenital malformations, such as oral-facial clefts. Smoking during pregnancy is consistently associated with an increased risk of sudden infant death syndrome (SIDS), with the risk being doubled or tripled in infants of daily smokers compared to nonsmokers. Smoking during pregnancy is also associated with increased risks of hospitalization and respiratory disorders in infancy and childhood. Maternal smoking during pregnancy is associated with increased risks of lower respiratory illnesses and childhood asthma. Smoking during pregnancy is also associated with increased risks of behavioral and psychiatric disorders in childhood. Smoking during pregnancy is associated with increased risks of perinatal mortality, including stillbirth and early neonatal mortality. Smoking is also associated with increased risks of placental abruption, placenta previa, and preterm birth. Smoking during pregnancy is associated with increased risks of gestational hypertension and preeclampsia, which are leading causes of maternal mortality in the United States. Smoking during pregnancy is associated with increased risks of congenital malformations, including oral