Over the last 30 years, the management of gestational diabetes mellitus (GDM) has evolved from an almost randomised controlled trial (RCT) “evidence-free” condition, based upon historical, clinical experience, to a much studied, and discussed, clinical entity with varied guidelines around the world. While the guidelines continue to converge, based upon RCTs and robust cohort studies, differences in views on “best practice” remain. The Diabetes and Pregnancy Vitamin D And Lifestyle Intervention for Gestational Diabetes Mellitus Prevention (DALI) studies have now provided insight into reasons why the existing paradigm, that GDM largely commences at 24-28 weeks, and management is directed by the oral glucose tolerance test (OGTT) at that time, is seriously flawed. In fact, for many years, studies have shown that GDM diagnosed early in pregnancy is associated with worse outcomes than pregnancies with GDM developing later in pregnancy. Such early, “booking” or “prevalent” GDM is about 40-60% of all GDM, and a new debate is how its diagnosis should take place. Another major issue is our dissatisfaction with the variation (and discomfort) associated with the OGTT, but the lack of a replacement test that assesses both existing glycaemia and risk of insulin secretory insufficiency, without confounding by other factors (eg red cell turnover with HbA1c). With the current precision of glucose monitoring, there appears to be an increasing unwritten acceptance of the principle, that rather than the OGTT being the gateway to specialist care, such triaging should often be guided by the glucose monitoring after the OGTT. New evidence (eg diagnostic criteria, glucose action thresholds) is urgently required to ensure that this paradigm shift improves pregnancy outcomes while minimising the burden on the women affected.