Kobayashi S, et al. - Using a highly sensitive ELISA method, researchers studied the association between plasma cotinine level measured at the 8th gestational month and the delivery of small-for-gestational-age (SGA), defined as a gestational age-specific weight Z-score below −2, infants. In this prospective birth cohort study from The Hokkaido Study on Environment and Children’s Health, 15,198 mother-infant pairs enrolled in 2003–2012. The increased risk of SGA was associated with a plasma cotinine level of ≥3.03 ng/mL, which included both passive and active smokers. This finding is important when educating pregnant women to avoid prenatal passive and active smoking due to the adverse effects on their children, even full-term born.