Preterm delivery and exposure to active and passive smoking during pregnancy: a case–control study from Italy.

The aim of this study was to assess the relationship between preterm/early preterm delivery and active smoking as well as environmental tobacco smoke (ETS) exposure in a sample of pregnant Italian women. A case–control study was conducted in nine cities in Italy between October 1999 and September 2000. Cases of preterm birth were singleton babies born before the 37th gestational week; babies born before the 35th gestational week were considered early preterm births. Controls were babies with gestational ages ≥ 37th week. A total of 299 preterm cases (including 105 early preterm) and 855 controls were analysed. A self-administered questionnaire was used to assess active smoking and ETS exposure, as well as potential confounders. Multivariable logistic regression analysis showed a relationship between active smoking during pregnancy and preterm/early preterm delivery [adjusted ORs: 1.53; 95% CI 1.05, 2.21 and 2.00; 95% CI 1.16, 3.45, respectively]. A dose–response relationship was found for the number of cigarettes smoked daily. The adjusted ORs were 1.54 and 1.69 for preterm babies and 1.90 and 2.46 for early preterm babies for 1–10 and >10 cigarettes/day respectively. ETS exposure was associated with early preterm delivery [adjusted OR 1.56; 95% CI 0.99, 2.46] with a dose–response relationship with the number of smokers in the home. Smoking during pregnancy was strongly associated with preterm delivery with a dose–response effect. ETS exposure in non-smoking women was associated only with early preterm delivery. [ABSTRACT FROM AUTHOR]