Secondhand smoke during the periconceptional period increases the risk for orofacial clefts in offspring

To examine whether exposure to secondhand smoke (SHS) during the periconceptional period among nonsmoking women is associated with an increased risk for orofacial clefts (OFCs) in offspring in a population with low rates of maternal active smoking but high rates of SHS exposure.

We recruited 240 women with OFC-affected pregnancies and 1420 women who delivered healthy infants from a population-based case-control study in northern China during 2002 and 2016. Data including self-reported SHS exposure were collected by trained health care workers through face-to-face interviews. Odds ratios (ORs) with 95% confidence intervals (95% CIs) were used to estimate the association between SHS exposure and OFC risk.

The unadjusted ORs for OFCs and cleft lip with or without cleft palate (CL±P) in association with SHS exposure were both 1.6 (95% CI 1.2, 2.1). After adjusting for maternal fever or flu, farming occupation, infant sex, and history of pregnancy affected by birth defects, the adjusted ORs were both 1.6 (95% CI 1.2, 2.2). Frequent SHS exposure (>6 times/week) was associated with an even higher risk for OFCs (adjusted OR 2.6, 95% CI 1.8, 3.8) and for CL±P (adjusted OR 2.5, 95% CI 1.7, 3.7).

Maternal SHS exposure during the periconceptional period increases the risk for OFCs in offspring among nonsmoking mothers.