Women who smoke during pregnancy have a greater risk of placental abruption than those who do not, researchers report in the August issue of the 

Cande V. Ananth and Sven Cnattingius of the University of Medicine and Dentistry of New Jersey in New Brunswick, NJ, performed a population-based prospective cohort study of 526,690 women who delivered their first two consecutive births in Sweden in 1983–2001. 

Women who smoked during pregnancy had almost double the risk of abruption in a second pregnancy (OR, 1.8), but not the first pregnancy. Women who had an abruption in a first pregnancy had an 11-fold higher risk of abruption in a second pregnancy if they smoked (OR, 10.9). However, women who had an abruption in a first pregnancy had a higher risk for abruption in the second pregnancy irrespective of their smoking history. 

Ananth CV, Cnattingius S. Influence of maternal smoking on placental abruption in successive pregnancies: a population-based prospective cohort study in Sweden. 