What diet to recommend before pregnancy to reduce the risk of gestational diabetes and during pregnancy to affect its course and improve perinatal outcomes? A review of the current evidence.

Several dietary strategies are designed to achieve optimal glycaemic control in managing gestational diabetes mellitus (GDM), considering factors such as energy needs, the glycaemic index, high fibre content and the reduction or exclusion of sugary foods and drinks. However, in achieving therapeutic goals, there is a lack of consensus in the formulation of uniform recommendations. This article reviews the literature to assess the impact of dietary interventions on GDM risk - measured by the percentage of at-risk women who develop GDM - and on the progression of GDM pregnancies, including weight gain, hyperglycaemia severity, insulin requirements and perinatal outcomes such as macrosomia, hypertensive disorders, caesarean delivery and neonatal size. We conducted a thorough search of PubMed and the Cochrane Library, focusing on randomised controlled trials, cohort studies, systematic reviews and meta-analyses involving women either at risk of or diagnosed with GDM. These search criteria yielded 2800 articles, whose titles and abstracts were reviewed to determine their relevance to the research objective. In the initial search, 192 relevant articles met the inclusion criteria. The comprehensive analysis of these studies highlights the current uncertainty regarding the long-term consequences of recommended diets during pregnancy, especially among women with GDM. While the available literature is substantial, conclusions drawn from various methodologies and study populations have not yielded a consensus on the most effective diet for reducing perinatal complications. Nonetheless, it is reasonable to advocate for the early initiation of dietary interventions, particularly during pregnancy planning, especially among women exhibiting risk factors for GDM.