Passive smoking, adverse perinatal outcomes linked

Two recent studies confirm that passive, secondhand cigarette smoke inhaled by pregnant women increases the risks for stillbirth, certain birth defects, and other adverse perinatal outcomes.

The first study was a systematic review of 19 studies carried out in North America, South America, Asia, and Europe. All the studies focused on pregnant women exposed to smoking in the home by a partner or in the workplace by colleagues. The authors of the study found that passive smoke increased the risk for stillbirth by 23% (odds ratio [OR], 1.23; 95% CI, 1.09-1.38) and the risk for congenital birth defects by 13% (OR, 1.13; 95% CI, 1.01-1.26). They found no significant effect of secondhand smoke on the risk for spontaneous abortion (OR, 1.17; 95% CI, 0.88-1.54) or on the risk for perinatal or neonatal death.

The second study, a retrospective cohort study, included 11,852 women of whom 1,202 self-reported exposure to environmental tobacco smoke (ETS) and 10,650 did not. All were pregnant with singleton gestations and delivered between April 1, 2001, and March 31, 2009, in Newfoundland and Labrador, Canada.

Finally, the exposed women were twice as likely to have babies with bacterial sepsis as those not exposed (1.08% vs 0.51%, respectively). Maternal exposure to ETS also was an independent risk factor for smaller head circumference (OR, -0.24 cm; 95% CI, -0.39 cm to -0.08 cm) and shorter birth length (OR, -0.29 cm; 95% CI, -0.51 cm to -0.07 cm).

Leonardi-Bee J, Britton J, Venn A. Secondhand smoke and adverse fetal outcomes in nonsmoking pregnant women: a meta-analysis. Pediatrics. 2011;127(4):734-741.

Crane J, Keough M, Murphy P, Burrage L, Hutchens D. Effects of environmental tobacco smoke on perinatal outcomes: a retrospective cohort study. BJOG. March 23, 2011. Epub ahead of print.