Controversies in gestational diabetes

Gestational diabetes mellitus (GDM) and controversy are old friends. However, several major studies in the field have clarified some of the main issues. There is now no doubt that hyperglycaemia, at levels less than those that occur in overt diabetes, is associated with adverse pregnancy outcomes, such as large-for-gestational age infants, neonatal hyperinsulinism, neonatal hypoglycaemia and pre-eclampsia. We also have evidence now that a standard approach to GDM with diagnosis at 24–28 weeks, dietary advice, self-monitoring of blood glucose and insulin therapy as needed reduces these adverse perinatal outcomes. Unknown, however, is if this same approach is effective at reducing long-term risks of metabolic syndrome, type 2 diabetes and cardiovascular disease in both the mothers and babies. For example, could our management strategies miss critical time points of fuel-mediated injury to the foetus important for the baby’s long-term metabolic health? The implications of a recent international consensus statement on new diagnostic criteria for GDM are discussed, as well as issues relating to the timing of diagnosis. The potential place for a risk calculator for adverse outcomes in GDM pregnancy that takes into account glycaemic and non-glycaemic risk factors is considered. Such a tool could help stratify GDM women to different levels of care. Ongoing issues relating to maternal glycaemic and foetal growth targets, and the use of oral hypoglycaemic agents in GDM are discussed. To resolve some of the remaining controversies, further carefully designed randomised controlled trials in GDM with long-term follow-up of both mothers and babies are necessary.