Paternal smoking and maternal secondhand smoke exposure and the effects on the offspring: results from the EHF (Environmental Health Fund) birth cohort

Background: Exposure during pregnancy to secondhand smoke (SHS) is associated with a wide range of adverse fetal development effects and perinatal outcomes. This study aimed to measure SHS exposure in pregnant women using urinary cotinine measurements and to evaluate the association between paternal smoking and maternal urine cotinine and birth outcomes in a birth cohort of Israeli mothers and children. Methods: We measured cotinine in urine samples taken at birth from 96 non-smoking mothers participating in the EHF (Environmental Health Fund)-Assaf-Harofeh-Ichilov cohort. Half of the partners were smokers, based on the self-reported data. Logistic regression models were used to predict maternal urinary cotinine levels, and potential confounders were included in the model. We analyzed the association between maternal urinary cotinine levels and birth weight. Results: In our study of 96 nonsmoking pregnant women, 94% of women with a smoking partner and nearly 60% of those with a non-smoking partner were exposed to SHS and had urine cotinine levels above the Limits of Quantification (LOQ). Paternal smoking was a significant predictor for maternal urinary cotinine levels above the LOQ (aOR 7.83 95%CI [2.01–30.57], p-value = 0.003). There were no statistically significant differences between the birth outcomes (e.g. gestational age, birth weight, birth length, head circumference, and the delivery method) tested in both groups– self-reported smoking status and exposed vs. non-exposed newborns. Maternal urinary cotinine levels were inversely associated with newborns’ birth weight (beta estimate − 281.39, p-value = 0.048). When stratified by sex, in male newborns, maternal urinary cotinine was inversely associated with newborns’ birth weight (beta estimate 470.22, p-value = 0.014), but not in females. Conclusions: Our findings support the fact that partners are one of the primary sources of maternal secondhand smoke and may play an essential role in creating and maintaining smoke-free environments. Trial registration: ClinicalTrials.gov, ID: NCT03084445. Registered 06 February 2014, https://clinicaltrials.gov/study/NCT03084445.