Active and Passive Smoking and Fecundability in Danish Pregnancy Planners
Abstract
Objective To investigate the extent to which fecundability is associated with active smoking, time since smoking cessation, and passive smoking. Design Prospective cohort study. Setting Denmark, 2007–2011. Patients 3,773 female pregnancy planners aged 18–40 years. Intervention None. Main Outcome Measures Self-reported pregnancy. Fecundability ratios (FR) and 95% confidence intervals (CI) were estimated using a proportional probabilities model that adjusted for menstrual cycle at risk and potential confounders. Results Among current smokers, smoking duration ≥10 years was associated with reduced fecundability compared with never smokers (FR=0.85, 95% CI: 0.72–1.00). Former smokers who had smoked ≥10 pack-years had reduced fecundability regardless of when they quit smoking (1–1.9 years FR=0.83, 95% CI: 0.54–1.27; ≥2 years FR=0.73, 95% CI: 0.53–1.02). Among never smokers, the FRs were 1.04 (95% CI: 0.89–1.21) for passive smoking in early life and 0.92 (95% CI: 0.82–1.03) for passive smoking in adulthood. Conclusions Among Danish pregnancy planners, cumulative exposure to active cigarette smoking was associated with delayed conception among current and former smokers. Time since smoking cessation and passive smoking were not appreciably associated with fecundability.
How strong is the evidence?
Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence.
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