Maternal Smoking and Preterm Birth Among Infants With Orofacial Clefts.

ObjectiveTo evaluate the associations between maternal cigarette smoking and preterm birth (PTB) among infants with orofacial clefts (OFCs).DesignPopulation-based retrospective cohort study.SettingUsing data from the National Birth Defects Prevention Study (NBDPS, 1997-2011 deliveries) and the Birth Defects Study To Evaluate Pregnancy exposureS (2014-2021 deliveries), we evaluated the association between maternal smoking and PTB (<37 weeks) among liveborn infants with cleft lip with/without cleft palate (CL±P), cleft palate only (CP), or any OFC.ParticipantsIn total, 5618 liveborn infants with OFCs (3699 CL±P and 1919 CP).Main Outcome Measure(s)Adjusted relative risks (aRRs) and 95% confidence intervals (CIs) were calculated using Poisson regression, adjusted for covariates. For each OFC group, smoking (any vs none) was evaluated during 5 pregnancy timepoints (eg, first trimester). Analyses were repeated for smoking intensity (none, 1-14, ≥15 cigarettes/day) (NBDPS only). Any smoking and smoking intensity were also evaluated for extremely-to-very (<32 weeks) and moderate-to-late preterm (32 to <37 weeks).ResultsAmong infants with OFCs, 14.5% were born preterm. Heavy smoking (≥15 cigarettes/day vs none) in the second trimester was associated with PTB among infants with CP (aRR: 1.89, 95% CI: 1.03-3.45) and extremely-to-very PTB among infants with any OFC (aRR: 3.37, 95% CI: 1.47-7.73). Associations were generally stronger for CP than for CL±P, though imprecise.ConclusionsHeavy smoking during the second trimester may increase the risk of extremely-to-very PTB in infants with OFCs and PTB among infants with CP, further supporting the importance of promoting maternal smoking cessation or reduction.