Aims — To evaluate the relationship between gestational diabetes and incidence of cancer in women within the first decade postpartum.
Methods — This population-based retrospective cohort study compared the risk of cancer in women with gestational diabetes with that of a matched control group comprising pregnant women without diabetes. We included women from Ontario, Canada aged 20–50 years with no history of cancer who had given birth between 1995 and 2008 (N=149,049). Women with gestational diabetes (N=49,684) were matched on age and year of giving birth, in a ratio of 1:2, to pregnant women without diabetes (N=99,365).
Results — Over a median 8-year follow-up, there were a total of 2,927 (1.5%) cancers. After adjustment for covariates, we found no significant difference in overall risk of cancer between women with gestational diabetes and matched control subjects; however, gestational diabetes was associated with a significantly greater risk of thyroid cancer (adjusted hazard ratio 1.24, 95% CI 1.05, 1.46) and a significantly lower risk of premenopausal breast cancer (hazard ratio 0.86, 95% CI 0.75, 0.98) compared with matched control subjects.
Conclusions — This large population-based study did not find a greater risk of cancers among women with gestational diabetes during the first decade postpartum; however, gestational diabetes was associated with a higher risk of thyroid cancer and a lower risk of premenopausal breast cancer. Further studies are needed to confirm these findings.