Meta-analysis of the association of maternal smoking and passive smoking during pregnancy with neural tube defects

Abstract

Background: It is unclear whether the incidence of neural tube defects (NTDs) is greater with maternal smoking or with passive smoking during pregnancy.

Objectives: To compare the effects of smoking and passive smoking during pregnancy on the risk of NTDs.

Search strategy: English and Chinese databases were searched for relevant papers published before March 2017, using search terms including "smoking" and "NTD."

Selection criteria: Case-control and cohort studies on the aforementioned association were included.

Data collection and analysis: Two authors independently extracted the original data. Meta-analyses were performed to assess the risks associated with smoking and passive smoking, followed by a comparison of the two pooled effect estimates. The I² statistic was used to examine between-study heterogeneity.

Main results: The final analysis included 23 articles representing 33 studies. The pooled odds ratio (OR) and 95% confidence interval (CI) for the risk of NTDs was 1.052 (0.907-1.220) with smoking and 1.898 (1.557-2.313) with passive smoking. Comparison of these ORs indicated that the risk of NTDs was higher with passive smoking than with smoking (OR 1.804, 95% CI 1.409-2.309).

Conclusions: Compared with smoking, exposure to passive smoking during pregnancy carries a higher risk of having infants with NTDs.

Keywords: Meta-analysis; Neural tube defects; Pregnancy; Smoking.