Liu B, Song L, Zhang L, et al. - Researchers examined if prenatal second-hand smoke exposure is associated with newborn telomere length. They obtained information on second-hand smoke exposure via questionnaires from 762 mother–newborn pairs from Wuhan Children’s Hospital (Wuhan Maternal and Child Healthcare Hospital) between November 2013 and March 2015. DNA extracted from umbilical cord blood was assessed for measuring relative telomere length. In the fully adjusted model, an association of prenatal second-hand smoke exposure with 9.7% shorter newborn telomere length was observed. For boys vs girls, the estimate was lower, however, the interaction term between newborn gender and prenatal second-hand smoke was not significant. Findings thereby establish prenatal second-hand smoke exposure as a preventable risk factor for accelerated biological aging in the intrauterine stage.