Treatment of gestational diabetes improves the health of the mother and her baby but it has remained unclear what degree of maternal hyperglycaemia is needed for the diagnosis.
The Gestational Diabetes Mellitus Trial of Diagnostic Thresholds (GEMS) compared the use of the lower glycaemic diagnostic criteria recommended by the IADPSG with the use of the higher glycaemic diagnostic criteria currently recommended in New Zealand. The trial assessed whether use of the lower criteria would improve perinatal health without increasing maternal risks compared with use of the higher criteria and to determine any differences in use of health services between the two criteria groups.
At the population level, amongst the 4061 women participating, use of the lower criteria compared with the higher criteria increased the proportion of women diagnosed with gestational diabetes two and a half fold but did not reduce perinatal morbidity and use of health services was increased. For women with milder gestational diabetes there were health benefits for them and their baby, relating to preeclampsia, shoulder dystocia, and birth of a large for gestational age infant, from detection and treatment.