Varying Impact of Gestational Diabetes Mellitus on Incidence of Childhood Cancers: An Age-Stratified Retrospective Cohort Study

OBJECTIVE: We studied the association between gestational diabetes mellitus and early versus late childhood cancer. RESEARCH DESIGN AND METHODS: We conducted a retrospective cohort study of 1 million children born between 2006 and 2019 in Quebec, Canada. We identified children who were exposed to gestational diabetes mellitus in utero and followed them from birth up to 14 years of age to identify new-onset cancers. We estimated hazard ratios (HRs) for the association between gestational diabetes mellitus and childhood cancer using Cox proportional regression models with adjustment for covariates through inverse propensity score weights. RESULTS: A total of 83,626 children (8.2%) were exposed to gestational diabetes mellitus, and 1,702 developed cancer during 7.6 million person-years of follow-up. Children exposed to gestational diabetes mellitus had a higher risk of any cancer (HR 1.19, 95% CI 1.01-1.40), with signals present for blood cancer (HR 1.27, 95% CI 0.92-1.76) and solid tumors (HR 1.14, 95% CI 0.94-1.40). The association between gestational diabetes mellitus and cancer was strongest early in life and decreased with age. Gestational diabetes mellitus was associated with 1.47 times the risk of any cancer (95% CI 1.21-1.79), 1.44 times the risk of solid cancer (95% CI 1.12-1.87), and 1.61 times the risk of blood cancer (95% CI 1.09-2.36) in children age 2 years. Gestational diabetes mellitus was not significantly associated with blood or solid cancers after 2 years of age, and all associations disappeared after 6 years. CONCLUSIONS: Hyperglycemia may be carcinogenic in utero and may be a novel risk factor for early childhood cancer.