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

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 I 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.