CONTEXT: The prevalence of Gestational Diabetes Mellitus (GDM) is increasing, and intrauterine hyperglycemia is suspected to affect offspring cognitive function.

OBJECTIVE: We assessed academic performance by grade point average (GPA) in children aged 15-16 years at compulsory school graduation, comparing offspring exposed to GDM (O-GDM) with offspring from the background population (O-BP).

DESIGN: Cohort study.

SETTING: Register-based.

PARTICIPANTS: All singletons born in Denmark between 1994 and 2001 (O-GDM: n=4,286; O-BP: n=501,045). Standardized and internationally comparable GPAs were compared in univariate- and multivariate linear models.

MAIN OUTCOME MEASURES: Adjusted mean difference in GPA. We additionally analyzed the probability of having a high GPA, a GPA below passing, and no GPA registered.

RESULTS: O-GDM had a GPA of 6.29 (SD 2.52), while O-BP had a GPA of 6.78 (SD 2.50). The adjusted mean difference was -0.36 [95% confidence interval (CI) -0.44; -0.29], corresponding to a Cohens D of 0.14. O-GDM had a lower probability of obtaining a high GPA (adjusted odds ratio (aOR) 0.68 [95 CI 0.59; 0.79]), while their risk of obtaining a GPA below passing was similar to O-BP (aOR 1.20 [95 CI 0.96; 1.50]). O-GDM had a higher risk of not having a GPA registered (aOR of 1.38 [95% CI 1.24; 1.53]).

CONCLUSION: Academic performance in O-GDM was marginally lower than in O-BP. However, this difference is unlikely to be of clinical importance.