Population-based cohort study of cancer chemotherapy during pregnancy and adverse neonatal outcomes

Administration of chemotherapy during pregnancy is often delayed, while preterm delivery is common. If in utero exposure to chemotherapy is associated with adverse pediatric outcomes, it is unknown whether that relationship is directly attributable to the chemotherapy or is mediated by preterm birth. A population-based cohort study in three Canadian provinces found that of 1150 incident cases of cancer during pregnancy, 142 (12.3%) received chemotherapy during pregnancy. In utero exposure to chemotherapy was associated with a higher risk of severe neonatal morbidity and mortality (SNM-M; RR 1.67; 95% CI 1.13-2.46) but not neurodevelopmental disorders and disabilities (HR 0.93; 95% CI 0.71-1.22) or pediatric complex chronic conditions (0.96; 0.80-1.16). Preterm birth before 34 weeks and 37 weeks of pregnancy mediated 75.8% and 100% of the observed association between chemotherapy exposure and SNM-M, respectively. The authors conclude that most children born to women with cancer during pregnancy have favorable long-term outcomes, even following exposure to chemotherapy in pregnancy. However, preterm birth is common, and may contribute to increased rates of neonatal outcomes.