This systematic review and meta-analysis investigated the effectiveness of pre-pregnancy lifestyle in preventing gestational diabetes mellitus (GDM). 30 studies (257,876 pregnancies) were included. Meta-analysis of randomized controlled trials (RCTs) showed a non-significant reduction in GDM risk (OR 0.76, 95% CI: 0.50–1.17, p = 0.21). However, meta-analysis of cohort studies revealed that pre-pregnancy physical activity, low carbohydrate/low sugar diets, and higher quality diet scores were associated with a reduced GDM risk (ORs ranging from 0.71 to 0.72). The limited number of RCTs, especially from low- and middle-income countries, highlights the need for further research.
