In cases where the mother has a mutation in the GCK gene and the fetus does not have a mutation in the GCK gene (or it is not implied), achieving adequate glycemic control is challenging due to the mother experiencing higher fasting and postprandial glycemic fluctuations in the first trimester compared to pregnant patients with HNF1A-MODY, despite the use of insulin therapy. Here, GCK is linked to MODY.