Individuals with HNF1A MODY, HNF4A MODY and KCNJ11/ABCC8 permanent neonatal diabetes can achieve excellent control on sulfonylureas outside pregnancy, and glycaemic control may be better on sulfonylureas than insulin 1, 2, 3, 4, 5; however, given that glibenclamide treatment increases the risk of macrosomia and neonatal hypoglycaemia, its use in pregnancy in women with monogenic diabetes needs to be reconsidered. The gene discussed is HNF1A; the disease is diabetes mellitus.