OBJECTIVES: Gestational diabetes is diagnosed using an oral glucose tolerance test (OGTT), which has limited accuracy, reproducibility and practicality. We assessed the effect of enhanced pre-analytical glucose processing upon glucose concentrations, gestational diabetes diagnosis, health equity and pregnancy outcomes, and if HbA1c was a suitable alternative. METHODS: We recruited pregnant women with ≥1 risk factor to a prospective observational cohort study of pregnancy hyperglycaemia, endocrine causes, lipids, insulin and autoimmunity (OPHELIA), from nine UK centres. During a 75 g antenatal OGTT (National Institute of Health and Care Excellence criteria), standard glucose processing was compared to enhanced glucose processing (storage on ice, rapid centrifugation, aliquoting and freezing <
2.5 h). RESULTS: We recruited 1308 participants of mean (SD) age 31.5 years (5.0) and BMI 33.0 kg/m CONCLUSIONS: An OGTT with enhanced glucose processing would support more accurate, equitable diagnosis of gestational diabetes, but with increased diagnosis rates.