Maturity-onset diabetes of the young (MODY) is the most common monogenic form of diabetes, accounting for 1-2% of all diabetes cases. At least 14 different MODY subtypes have been identified the most common of which is MODY 2 caused by mutations in the glucokinase (GSK) gene. The mild hyperglycemia of MODY 2 is often first detected during pregnancy. Patients with MODY are usually misdiagnosed as either idiopathic type 1 or type 2 diabetes. The recognition of MODY 2 during pregnancy has important clinical implications as the management of hyperglycemia may differ from the established algorithm in gestational diabetes. Fetus development could be seriously affected in case it has inherited the GSK mutation and maternal hyperglycemia is insulin treated to the pregnancy adopted glycemic targets. The case report describes the stepwise diagnostic approach to a 43-year-old woman with a history of gestational diabetes and persistent prediabetes who was found to be a carrier of a heterozygous pathogenic variant in GSK (c.184G>A) and discusses the possible genotype of her two children according to their birth weight.
