The effects of prenatal secondhand smoke exposure on preterm birth and neonatal outcomes

Objective: To examine the relationship between prenatal secondhand smoke (SHS) exposure, preterm birth and immediate neonatal outcomes by measuring maternal hair nicotine. Design: Cross-sectional, observational design. Setting: A metropolitan Kentucky birthing center. Participants: Two hundred and ten (210) mother-baby couplets. Methods: Nicotine in maternal hair was used as the biomarker for prenatal SHS exposure collected within 48 hours of birth. Smoking status was confirmed by urine cotinine analysis. Results: Smoking status (nonsmoking, passive smoking, and smoking) strongly correlated with low, medium, and high hair nicotine tertiles (ρ=74; p<001). Women exposed to prenatal SHS were more at risk for preterm birth (odds ratio [OR]=2.3; 95% Confidence Interval [CI] [.96, 5.96]), and their infants were more likely to have immediate newborn complications (OR=2.4; 95% CI [1.09, 5.33]) than nonexposed women. Infants of passive smoking mothers were at increased risk for respiratory distress syndrome (RDS) (OR=4.9; 95% CI [1.45, 10.5]) and admission to a Neonatal Intensive Care Unit (NICU) (OR=6.5; CI [1.29, 9.7]) when compared to infants of smoking mothers (OR=3.9; 95% CI [1.61, 14.9]; OR=3.5; 95% CI [2.09, 20.4], respectively). Passive smokers and/or women with hair nicotine levels greater than .35 ng/ml were more likely to deliver earlier (1 week), give birth to infants weighing less (decrease of 200-300 g), and deliver shorter infants (decrease of 1.1-1.7 cm). Conclusions: Prenatal SHS exposure places women at greater risk for preterm birth, and their newborns are more likely to have RDS, NICU admissions, and immediate newborn complications.