At Rigshospitalet, Copenhagen, Denmark, pregnancy management for women with GCK-MODY is guided by markedly elevated glucose levels and fetal overgrowth, while management for women with HNF1A-MODY follows guidelines for type 1 and type 2 diabetes. We aimed to evaluate current treatment strategies for pregnant women with GCK- or HNF1A-MODY.

We conducted a retrospective population-based cohort study of 18 consecutive pregnancies in 11 women with GCK-MODY and 17 consecutive pregnancies in 11 women with HNF1A-MODY, matched with 140 pregnancies in 133 women with type 2 diabetes, referred to Rigshospitalet, Copenhagen, between June 2011 and December 2023. Glycemia, pregnancy- and perinatal outcomes were compared using generalized estimating equation models.

In pregnancies in women with GCK-MODY, median HbA1c levels remained stable from early in pregnancy (< 20 weeks) to late in pregnancy (45 to 46 mmol/mol), while decreasing in pregnancies in women with HNF1A-MODY (41 to 37 mmol/mol) and type 2 diabetes (47 to 41 mmol/mol). The prevalence of hypertensive disorders (5.6 vs. 35.0 %), preterm delivery (0 % vs. 17.9 %), and large for gestational age (16.7 % vs. 35.7 %), were lower in pregnancies in women with GCK-MODY compared to type 2 diabetes, though not statistically significant. Pregnancy- and perinatal outcomes were comparable between pregnancies in women with HNF1A-MODY and type 2 diabetes.

In women with GCK-MODY, pregnancy outcomes were reassuring supporting the current treatment strategy. In women with HNF1A-MODY, guidelines for type 1 and type 2 diabetes resulted in glycemic control within target and pregnancy outcomes similar to type 2 diabetes.