BACKGROUND: Maternal diabetes may be linked to childhood acute lymphoblastic leukaemia (ALL) in the offspring.

METHODS: We assessed the association between maternal pregestational or gestational diabetes and offspring risk of childhood ALL in a register-based study, including all singletons born in Denmark during 1996-2015 (n=1 187 482).

RESULTS: Adjusted hazard ratios of childhood ALL were 2.91 (95% confidence interval (CI): 1.30-6.51) for maternal pregestational diabetes and 1.75 (95% CI: 1.02-2.98) for maternal gestational diabetes. Paternal diabetes did not alter offspring ALL risk, and we found no association between offspring ALL and later maternal risk of diabetes.

CONCLUSIONS: Regardless that absolute ALL risk among offspring of women with diabetes remains low, our findings suggest that characteristics of the diabetic intrauterine environment promote ALL development. This offers a setting for future research into the biological mechanisms underlying childhood ALL.