Abstract
Gestational diabetes mellitus (GDM) is associated with significant maternal and neonatal morbidity. Screening strategies vary internationally and the diagnostic performance of the 50g glucose challenge test (50g GCT) as a universal screening tool remains uncertain across diverse populations.
This retrospective cohort study included 18,213 singleton pregnancies at a London tertiary hospital between 2010 and 2023. Women routinely underwent the universal two-step GDM screening pathway: a 50g GCT at 24 - 32 weeks' gestation, followed by a diagnostic 75-g oral glucose tolerance test if the 50g GCT result was greater than or equal to 7.8 mmol/L. We evaluated the use of universal two-step screening in detecting GDM, how its prevalence varies with maternal characteristics, including ethnicity, body mass index, age, and in those who would not have been included in risk factor-indicated screening, and the association between the 50g GCT and adverse outcomes.
2,015 women had an abnormal GCT, and 406 (20.1%) had an abnormal 75g OGTT, with GDM diagnosed at 24-28 weeks. We also found 87 women, despite a normal GCT and/or normal OGTT, developed late-onset GDM. The overall prevalence of GDM was 4.4% (810/18,213). Universal screening will therefore identify a significant number of GDM cases, notably including those in a low-risk cohort who would not have been screened using a risk factor-based approach. When we examined glucose as a continuous variable, there was an association between increasing 50g GCT values and adverse maternal and neonatal outcomes.
Universal screening with a GCT is a feasible and safe approach and addresses a significant health disparity gap, in that women without risk factors are screened and may be diagnosed with GDM. Given the long-term cardiometabolic implications of GDM, pregnancy diagnosis is important to allow for longer-term targeting of cardiometabolic risk factors to improve long-term health screening for type 2 diabetes and obesity.