Gestational Diabetes Mellitus and Risk of Selected Cancers: A Danish National Register-based Cohort Study

Gestational diabetes mellitus (GDM) is the most common medical complication of pregnancy and is associated with type 2 diabetes, which is associated with breast cancer and kidney cancer. However, little is known about the risk of cancer following a GDM diagnosis.

This study aimed to test the hypothesis that a history of GDM associates with increased risk of breast, gynecological, thyroid, and kidney cancer.

National cohort study, based on Danish registry data. The study population included a group of women exposed to GDM in their pregnancy leading to delivery between 2000 and 2019 or 1978 and 1997 and a 1:10 matched nonexposed group, matched on calendar period of delivery, the woman´s age (birth year), and the woman´s registered region of residence at delivery. Poisson regression adjusting for educational level was conducted.

Of the 314 742 deliveries included, 28 613 deliveries were in the exposed group and 286 129 in the nonexposed. The median follow-up time was 8.1 years. We found no increased risk of the selected cancers combined [adjusted incidence rate ratio (aIRR) 1.05; 95% confidence interval (CI), 0.94-1.18], breast cancer (aIRR 1.02; 95% CI, 0.89-1.17), gynecological cancer (aIRR 1.00; 95% CI, 0.79-1.26), or thyroid cancer (aIRR 1.26; 95% CI, 0.86-1.82). However, an increased risk of kidney cancer was seen in women with previous GDM compared with women without GDM (aIRR 1.92; 95% CI, 1.10-3.33), although it was a very small absolute risk.

No elevated risk was found for the selected cancers combined. Women with previous GDM had an increased risk of kidney cancer, a rare cancer form.