Exposure to second-hand smoke and reproductive outcomes depending on maternal asthma

Tobacco consumption and exposure to second-hand smoke (SHS) are associated with reduced birth weight. One issue that has not been clarified previously is that of the potential higher risk of this outcome in mothers with asthma. We assessed the role of prenatal maternaltobacco use and SHS on reproductive outcomes and assessed the interaction with maternalhistory of asthma. Data was collected from the INMA study, a maternalbirth cohort selected from the general population established in Spain in 2002. We measured cotinineat the 32nd week of pregnancy in 2,219 females. Diagnosed maternal asthmawas self-reported during pregnancy. 35% of mothers reported not being exposed to smoking or SHS during pregnancy. Active smoking ( i.e. self-reported or cotinine>50 ng·mL −1 ) was related to a 134 g decrease in birth weight and a relative risk of 1.8 for smallfor gestational ageand fetal growth restriction. These results were not modified by maternal asthma. Maternal asthmahad a similar frequency in all exposure groups. Non SHS-exposed females had the lowest prevalence of asthma. SHS ( i.e. cotinine20–50 ng·mL −1 ) decreased birth weight by 32 g among those without maternal asthma, but these differences were not statistically significant (95% CI -88.76–24.76). Maternal asthmadid not promote these effects. Maternalhistory of asthmadid not modify the effects of smoking on reproductive outcomes in a cohort sampled from the general population.