Association between Heated Tobacco Product Use during Pregnancy and Fetal Growth in Japan: A Nationwide Web-Based Survey

Combustible cigarette smoking impacts fetal growth during pregnancy. However, the risk associated with heated tobacco products (HTPs) remains unclear. This nationwide cross-sectional study investigated whether HTP use during pregnancy is associated with small for gestational age (SGA) outcomes among 5647 post-delivery women with singleton pregnancies, which were divided into four groups: lifetime never-smokers, former smokers before pregnancy, and current smokers for each of the tobacco products during pregnancy (sole HTP and sole combustion smokers). Information on the prevalence of SGA, defined as birth weight and height below the 10th percentile, was retrieved from the Maternal and Child Health Handbooks of post-delivery women. Using logistic regression, the association between sole HTP smokers during pregnancy and SGA, adjusted for covariates, with lifetime never-smokers as reference, was investigated. The prevalence was: current sole HTP smokers during pregnancy, 1.8% (102/5647); and SGA, 2.9% (164/5647). Sole HTP smokers during pregnancy had a higher prevalence of SGA (5.9% [6/102] vs. 2.7% [111/4144]) with an adjusted odds ratio (OR) of 2.50 (95% confidence interval [CI], 1.03–6.05) than lifetime never-smokers. Among sole combustion smokers, the adjusted OR for SGA was 1.95 (95% CI, 0.81–4.67). In Japan, HTP smoking during pregnancy may be associated with an increased risk for SGA.