Effects of environmental tobacco smoke on perinatal outcomes: a retrospective cohort study

Objective: To evaluate the effects of environmental tobacco smoke (ETS) on perinatal outcomes.

Design: Retrospective cohort study.

Setting: Newfoundland and Labrador, Canada.

Population: Nonsmoking women with singleton gestations who delivered 1 April 2001-31 March 2009, identified through the Newfoundland and Labrador Provincial Perinatal Database.

Methods: Women who self-reported exposure to ETS were compared with those who reported no exposure. Univariate analyses and multivariate linear and logistic regression analyses (adjusting for maternal age, parity, partnered status, work status, level of education, body mass index, alcohol use, illicit drug use and gestational age) were performed and odds ratios(OR; or adjusted differences) with 95% confidence intervals were calculated.

Main outcome measures: Birthweight, birth length, head circumference and stillbirth. Secondary outcomes included gestational age at delivery, preterm birth <37 and <34 weeks of gestation, prelabour rupture of membranes, Apgar score, endotracheal intubation for resuscitation, neonatal intensive care unit admission, congenital anomalies, respiratory distress syndrome, intraventricular haemorrhage, neonatal bacterial sepsis, jaundice and neonatal metabolic abnormalities.

Results: A total of 11,852 women were included: 1202(11.1%) exposed to ETS and 10,650 (89.9%) not exposed. Exposure to ETS was an independent risk factor for lower mean birthweight (-53.7 g, 95% CI -98.4 to -8.9 g), smaller head circumference (-0.24 cm, 95% CI -0.39 to -0.08 cm), shorter birth length (-0.29 cm, 95% CI -0.51 to -0.07 cm), stillbirth (OR 3.35, 95% CI 1.16-9.72, P = 0.026), and trends towards preterm birth <34 weeks (OR 1.87, 95% CI 1.00-3.53, P = 0.05) and neonatal sepsis (OR 2.96, 95% CI 0.99-8.86).

Conclusions: Exposure of nonsmoking pregnant women to ETS is associated with a number of adverse perinatal outcomes including lower birthweight, smaller head circumference and stillbirth, as well as shorter birth length. This information is important for women, their families and healthcare providers, and reinforces the continued need for increased public policy and education on prevention of exposure to ETS.