Tobacco Exposure During Pregnancy and Infections in Infants up to 1 Year of Age: The Japan Environment and Children's Study.

Background: Tobacco exposure during pregnancy is associated with several adverse outcomes in infants. We investigated the association between tobacco exposure during pregnancy (both active and second-hand) and various infections in infants up to 1 year.
Methods: This prospective cohort study used a fixed dataset (jecs-an-20180131) from the Japan Environment and Children's Study of registered births in Japan during 2011-2014 that included 104,065 fetal records from enrolled pregnant women. Based on the participants' responses to the questionnaire on smoking status, mothers were first divided into "never smoked," "quit smoking," and "current smoker" groups and then into "no second-hand smoking (SHS)" and "SHS" groups. Infectious diseases included central nervous system infection, otitis media (OM), upper respiratory tract infection (URTI), lower respiratory tract infection (LRTI), gastroenteritis (GI), and urinary tract infection. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated using logistic regression analysis and adjusted for maternal, socioeconomic, and postnatal confounding factors.
Results: Among the 73,205 newborns enrolled, multivariable analysis revealed that the aOR of LRTI and GI was 1.20 (95% CI, 1.07-1.33) and 1.18 (95% CI, 1.04-1.35), respectively, for the "current smoker with/without SHS" group compared with the "never smoked without SHS" group. "Quit smoking without SHS" was not associated with the risk of LRTI. SHS was associated with an increased risk of OM, URTI, LRTI, and GI, especially with LRTI and GI.
Conclusion: Exposure to tobacco smoke during pregnancy was associated with an increased risk of OM, URTI, LRTI, and GI in infants during their first year of life.