Preconception Interventions in Women at High Risk of Developing Gestational Diabetes: A Systematic Review

Gestational diabetes mellitus (GDM) is a common pregnancy-related complication. The modest benefits of interventions to prevent GDM in women with high risk during pregnancy has shifted the focus to the preconception period. However, research on the effectiveness of preconception interventions in women who are more likely to develop GDM is lacking. This review aimed to assess the effect of preconception interventions, including behavioural strategies, supplementation, and pharmacological treatments on reducing the incidence of GDM. MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials were first searched in February 2023 and updated in December 2025 (PROSPERO CRD42020177976). Randomised controlled trials (RCTs) evaluating dietary/physical activity (PA)/combined, nutritional supplementation or pharmacological intervention in the pre-pregnancy period in women at high risk of developing GDM conducted in any country and reported in English were included. The pre-pregnancy period was defined as the period before and/or between pregnancies. A narrative synthesis was conducted in line with the Synthesis Without Meta-analysis guidelines, and each study was assessed using the Cochrane risk of bias tool. Six RCTs, equating to nine publications (n = 909 participants in total) were included. Two interventions were conducted during the pre-pregnancy period and discontinued upon conception, and the remaining four were delivered pre-pregnancy and continued throughout pregnancy. Five trials focused on modifying both dietary intake and PA and one trial modified diet only. No studies reported a significant effect of preconception behaviour change intervention on GDM development; however, five of the trials were underpowered to do so. Limited evidence fitted this review’s inclusion criteria, highlighting a considerable research gap. Future well designed, adequately powered RCTs of behaviour change and/or pharmacotherapy in women at higher risk for developing GDM are necessary to inform preconception care guidelines to improve the immediate and long-term health of women and their infants. The modest benefits of intervention to prevent GDM during pregnancy in women at higher risk has shifted focus to the preconception period, highlighting the need for early intervention to reduce pregnancy complications and long-term maternal and child health risks. Additionally, preconception health is suboptimal among women at increased risk of GDM, including those living with overweight or obesity or with a history of GDM. This review evaluated interventions to reduce GDM which were initiated in the preconception period and highlights a critical evidence gap. Only six RCTs were identified and while the findings suggest that preconception diet and physical activity intervention shows some benefits, impact on GDM prevention remains uncertain due to underpowered studies. This review highlights the urgent need for adequately powered RCTs that specifically target the preconception period in women likely to develop GDM. Research gaps on pharmacological interventions to address preconception obesity were also identified in this review.