The World Health Organization (WHO) identifies tobacco use as a major global health threat. Cigarette smoking during pregnancy is linked to poor birth outcomes (spontaneous abortion, low birth weight, pre-term birth). Children born to mothers who smoke often face long-term health and developmental challenges.
Secondhand smoke (SHS) or environmental tobacco smoke (ETS) poses significant risks to both maternal and fetal health. The present pregnancy risk of stillbirth and congenital malformation due to SHS prenatal exposure is 23% and 13% respectively, without considering the effects of maternal and fetal tobacco exposure among smoking mothers. Although the mother may not be a smoker, passive exposure to smoking by other people may affect the health of the fetus negatively. To evaluate the impact of paternal smoking, researchers from Shamir Medical Center and Tel Aviv Medical Center investigated whether exposure to secondhand smoke from fathers affected newborn health outcomes.
In this study, the researchers analyzed data associated with 96 non-smoking Israeli women who gave birth between 2013 and 2015. These women and their partners were part of the Environmental Health Fund (EHF) birth cohort that is part of a larger study. The demographic information of the mother and maternal smoking behavior was ascertained based on questionnaires and evaluation of recent exposure to tobacco smoke through quantification of the cotinine concentrations in maternal urine. At birth, newborn health outcomes such as birth weight and other vital outcomes were recorded. The mothers were classified into two groups according to the smoking status of their partner (smokers vs non-smokers). Researchers also quantified the cotinine, comparing it to the urine, and split the women into higher and lower than the limit of quantification (LOQ) set at 0.5 ng/mL.
The results were striking. Only 94.1% of women with a smoking partner had detectable cotinine levels above the LOQ that indicate recent exposure to secondhand smoke. Even in situations when 57.8% of women were in a non-smoking cohabitating situation in which the partner was not smoking, these still had elevated cotinine levels, which implicates other sources of exposure like shared buildings in the neighbourhood.
The mean urine cotinine level in women living with non-smoking partners was 0.57 ng/mL, and it was 1.07 ng/mL with smoking partners. When adjusted for dilution (creatinine), the mean cotinine levels were 1.16 mcg/g with non-smoking partners and 2.09 mcg/g with smoking partners (p < 0.001).
Logistic regression analysis revealed that paternal smoking increased the likelihood of maternal cotinine levels exceeding the LOQ by more than sevenfold (adjusted Odds Ratio = 7.83, 95% CI [2.01-30.57], p = 0.003). Partners with academic education were less likely to expose their partners to SHS, although this trend was only marginally significant (aOR 0.27, 95% CI [0.072-1.02], p-value = 0.053).
Notably, higher cotinine levels were associated with lower birth weights. With every increase in maternal cotinine, the baby’s birthweight decreased by an estimated 281.39 (p = 0.048). When examining the data by sex, this finding was significant in male infants only, who exhibited a weight decrease of 470.22 (p = 0.014) with higher levels of maternal cotinine.
The research highlights that secondhand smoke (SHS) from male partners has harmful effects on pregnant women’s and their babies’ health, such as lower birthweight, especially in male children. The researchers recognize these adverse changes in birth outcomes as a call for increased public health actions to facilitate smoke-free homes and communities, including engaging fathers in quitting smoking and intervening to limit human exposure to SHS in shared living units. Rather than a narrow focus on quitting as an individual and personal responsibility, there needs to be a larger change for households and communities to improve birth outcomes.
References: Berlin M, Kohn E, Keidar R, et al. Paternal smoking and maternal secondhand smoke exposure and the effects on the offspring: results from the EHF (Environmental Health Fund) birth cohort. Isr J Health Policy Res. 2025;14:41. doi:10.1186/s13584-025-00706-3
