Monogenic diabetes caused by GCK gene mutation is misdiagnosed as gestational diabetes - A multicenter study in Portugal

Abstract Aims Monogenic diabetes is an underdiagnosed type of diabetes mellitus, which can be harmful in pregnancy. We aim to estimate the prevalence of diabetes caused by the mutation of the glucokinase gene (GCK-MODY) in pregnant women diagnosed with gestational diabetes mellitus (GDM) and to characterize pregnant women with this suspicion. Methods A multicenter observational study with data prospectively collected from pregnancies with GDM was conducted. Two groups of pregnant women were considered: those with GCK-MODY criteria and those without those criteria. Results Of 18421 women with GDM, 3.6% (n = 730) had the GCK-MODY clinical criteria. A prevalence of 1.5% of GCK-MODY is estimated in women with GDM in Portugal, which is higher than in Northern European countries. Suspected GCK-MODY women had statistically higher odds of having neonates below the 25th percentile (OR = 1.23, 95%CI = 1.04–1.46, p = 0.016) and having prediabetes and diabetes in postpartum reclassification (OR = 2.11, 95%CI = 1.55–2.82, p  Conclusions Higher odds of neonates below the 25th percentile was probably due to excessive insulin treatment in cases where both the mother and the fetus have the mutation. It is essential to consider the diagnosis of GCK-MODY in all women with GDM criteria for better management of diabetes in pregnancy.