Gestational diabetes mellitus (GDM) is rising worldwide. Australia and New Zealand have had universal screening for GDM at 24-28 weeks’ gestation for many years. First trimester risk assessment and diagnosis may facilitate early interventions to protect the mother and fetus from short- and long-term adverse effects of weeks of hyperglycaemia.
We developed a 3-tier risk prediction algorithm in 2,832 women from the Adelaide and Auckland SCOPE cohorts, recruited in 2004-2008. The algorithm classifies women at low, moderate and high risk for GDM and includes clinical, lifestyle and genetic variables. Here we aimed to validate the algorithm at ~12 weeks’ gestation in a new prospective cohort, the STOP Study, recruited in 2015-2018 in Adelaide. GDM was diagnosed at 24-28 weeks’ gestation with a 75g OGTT using WHO criteria.
Of 1,233 Adelaide STOP women, 197 (16.0%) developed GDM. Of 389 women classified at low risk, 32 women (8.2%) subsequently developed GDM. Of 746 women classified at moderate risk, 137 (18.4%) developed GDM, while 28 of the 98 women classified at high risk developed GDM (28.6%).
The incidence of GDM has increased remarkably to 16% in STOP women from 5% (using the same diagnostic criteria) in the Adelaide SCOPE women which does not appear to be explained by obesity and about which our research is ongoing.
We have now validated our model in a new prospective cohort recruited 10 years after that in which it was developed. This screening tool needs further validation but may enable early identification of women at risk. All women at moderate and high risk of GDM could be offered an early OGTT and dietary advice or therapy if diagnosed with GDM, while low risk women could be offered an OGTT at 28 weeks’ gestation as per routine care.