Dietary Intervention in Pregnant Women with Gestational Diabetes; Protocol for the DiGest Randomised Controlled Trial

Abstract

Gestational diabetes mellitus (GDM) annually affects 35,000 pregnancies in the United Kingdom, causing suboptimal health outcomes to the mother and child. Obesity and excessive gestational weight gain are risk factors for GDM. The Institute of Medicine recommends weight targets for women that are overweight and obese, however, there are no clear guidelines for women with GDM. Observational data suggest that modest weight loss (0.6-2 kg) after 28 weeks may reduce risk of caesarean section, large-for-gestational-age (LGA), and maternal postnatal glycaemia. This protocol for a multicentre randomised double-blind controlled trial aims to identify if a fully controlled reduced energy diet in GDM pregnancy improves infant birthweight and reduces maternal weight gain (primary outcomes). A total of 500 women with GDM (National Institute of Health and Care Excellence (NICE) 2015 criteria) and body mass index (BMI) ≥25 kg/m² will be randomised to receive a standard (2000 kcal/day) or reduced energy (1200 kcal/day) diet box containing all meals and snacks from 28 weeks to delivery. Women and caregivers will be blinded to the allocations. Food diaries, continuous glucose monitoring, and anthropometry will measure dietary compliance, glucose levels, and weight changes. Women will receive standard antenatal GDM management (insulin/metformin) according to NICE guidelines. The secondary endpoints include caesarean section rates, LGA, and maternal postnatal glucose concentrations.

Keywords: continuous glucose monitoring (CGM); diet; dietary intervention; gestational diabetes; large-for-gestational age; maternal obesity; maternal or gestational weight gain; neonatal growth; neonatal hypoglycaemia; neonatal outcomes; pregnancy; randomised controlled trial; study protocol.

Figure 1

DiGest (Dietary intervention in Gestational diabetes) protocol summary. Abbreviations: OGTT, oral glucose tolerance test; GDM, gestational diabetes mellitus; ANC, antenatal clinic; CGM, continuous glucose monitoring; TFEQ–18, three factor eating questionnaire 18; EQ5DL, EuroQol 5 dimension quality of life questionnaire; HbA1c, hemoglobin A1c; INTAKE24, dietary recall questionnaire over 24 h period; DXA, dual-energy X-ray absorptiometry scan; ADP–PEA, air displacement plethysmography pea pod.