The effects of maternal smoking exposure during pregnancy on postnatal outcomes: A cross sectional study

The purpose of this article was to evaluate the effect of maternal smoking exposure during pregnancy on postnatal outcomes.

This prospective study enrolled 278 pregnant women in the third trimester, who were asked to complete a questionnaire which included inquires about the nature and extent of smoking exposure during their pregnancy. In addition to the questionnaire, each study subject provided urine sample for the measurement of cotinine. Using data generated from this inquiry, we analyzed the association between maternal smoking exposure and birth outcomes.

From the 278 enrollees in this study, a minority of subjects (7.2%) smoked, while 40.6% of the study subjects were exposed to environmental tobacco smoke during pregnancy. There was significantly higher birth weight (3205.2 ± 373.1 vs 3089.7 ± 363.0 vs 2959.0 ± 403.7 g, p = 0.004), larger chest size (33.1 ± 1.7 cm vs 32.7 ± 1.5 cm vs 32.0 ± 1.7 cm, p = 0.009), higher bilirubin on postnatal day 3 (8.9 ± 1.6 vs 8.6 ± 1.5 vs 7.8 ± 1.4 mg/dL, p = 0.015), but lower maternal urinary cotinine level (83.7 ± 132.4 vs 153.2 ± 96.0 vs 800.5 ± 1027.8 μg/g creatinine, p < 0.001) in smoking-free status than in passive or active smoking status. Significant risks of birth weight < 2500 g (AOR 3.93 (95% CI 1.61-9.59), p = 0.003) and maternal urinary cotinine ≥ 143 μg/g creatinine (AOR 3.38 (95% CI 2.02-5.66), p < 0.001) were observed as smoking exposure increased. There was significantly higher birth weight (p = 0.048), larger chest size (p = 0.045), and higher bilirubin level on postnatal day 3 (p < 0.001) in the group with cotinine <143 μg/g creatinine than in the group with cotinine ≥ 143 μg/g creatinine.

Our results demonstrated that maternal smoking exposure during pregnancy is associated with low birth weight and small chest circumference. Although the incidence of active smoking in Taiwanese pregnant women is low, most of them are exposed to passive smoking environment. Further studies are required to evaluate useful interventions to enhance a smoking-free environment during pregnancy.