Incidence of gestational diabetes and inequalities in adverse pregnancy outcomes in England: contemporary, cross sectional observational study of 2.7 million births

Objectives: To quantify the incidence of gestational diabetes mellitus in England, determine inequalities in diagnoses and pregnancy outcomes, and assess the indirect effects of the covid-19 pandemic. Design: Contemporary, cross sectional observational study. Setting: Primary and secondary care data from NHS England, based on the Hospital Episode Statistics Admitted Patient Care dataset, 1 January 2018 to 31 December 2022. Participants: 2 314 365 women, aged 16-50 years, who gave birth to 2 758 170 babies in 184 hospitals. Main outcome measures: Rates of gestational diabetes, infants born small for gestational age or large for gestational age, and emergency caesarean births, summarised yearly and monthly, based on socioeconomic deprivation and ethnic group. Results: Diagnoses of gestational diabetes increased from about 8% in 2018 to >12% in 2022. The increase was greatest for individuals from non-white ethnic groups (23% for Asian women) or those living in deprivation (14%). Mothers from these backgrounds were also at greater risk of adverse pregnancy outcomes, such as emergency caesarean birth (odds ratio for black mothers 1.36, 95% confidence interval 1.34 to 1.38), preterm birth (odds ratio for deprived mothers 1.29, 1.27 to 1.31), or having an infant small for gestational age (odds ratio for Asian mothers 2.42, 2.39 to 2.45). Also, a diagnosis of gestational diabetes for these women was associated with an increase in the odds of preterm birth. Changes to screening methodology for gestational diabetes during the covid-19 pandemic had no significant effect on the number of diagnoses. Conclusions: The study found that one in eight mothers in England had a diagnosis of gestational diabetes, and that profound health inequalities exist in their outcomes. Strategies are urgently needed to provide and improve care for this high risk group, given the implications of gestational diabetes on the short and long term health outcomes for mothers and babies.