Trends, disparities, and pregnancy outcomes of gestational diabetes mellitus in North West London: A nine-year population-based cohort study

Background Gestational diabetes mellitus (GDM) affects approximately 1 in 20 pregnancies in England. North West London (NWL) serves a diverse population of 2.4 million with substantial ethnic and socioeconomic variation. However, population-level epidemiological evidence from NWL remains limited. This study aims to characterise GDM incidence, temporal trends, risk determinants, and associated pregnancy outcomes. Methods A retrospective population-based cohort study using routinely collected data from the Whole Systems Integrated Care database included all birth episodes from 2017 to 2025, categorised as GDM or non-GDM. Incidence per 1,000 births was calculated and temporal trends were analysed. Multivariable generalised estimating equation (GEE) logistic regression models were used to examine maternal risk determinants for GDM and pregnancy outcomes associated with GDM, while controlling for confounders and accounting for within-woman clustering across pregnancies. Results Among 172,332 births from 134,991 women, 18,892 (10.9%) were GDM-affected. Overall incidence was 109.6 per 1,000 births (95% CI: 108.2-111.1), rising from 80.5 per 1,000 births in 2017 to 138 per 1,000 births in 2025. Incidence increased with maternal age and deprivation (119 vs. 85.4 in most vs. least deprived quintiles). Asian women had the highest risk (aOR 2.27, 95% CI: 2.15–2.40) relative to White. GDM was associated with higher rates of labour induction (51% vs. 41%), caesarean delivery (47% vs. 36%), preterm birth (7.3% vs. 5.2%), greater maternity care costs (£4,674 vs. £3,971) and longer maternal length of stay (3 vs. 2 days). Conclusion The incidence of GDM in NWL substantially exceeds national estimates and has nearly doubled over nine years, with pronounced ethnic and socioeconomic disparities. Targeted culturally appropriate prevention strategies and equity-focused service planning are needed in this population.