Gestational diabetes mellitus (GDM), hyperglycemia first detected during pregnancy, affects approximately 1 in 6 live births globally, with a higher prevalence in low- and middle-income countries (LMICs). This poses a significant public health concern, given GDM's association with adverse maternal and fetal outcomes, including increased risk of type 2 diabetes in both mother and offspring. Current management strategies primarily focus on diagnosis and treatment, achieving only a 50% reduction in short-term complications. A shift toward prevention is crucial to mitigate long-term risks and improve maternal and child health. Lifestyle interventions have proven effective in preventing type 2 diabetes, suggesting their potential role in GDM prevention. However, the effectiveness of lifestyle interventions during pregnancy has yielded mixed results. Interventions initiated in the early weeks of gestation show promise, but pre-conceptional interventions could potentially prevent adverse metabolic programming from the earliest stages. Previous studies on pre-pregnancy lifestyle interventions have been small, varied in quality, and under-represented in LMICs. This systematic review aimed to comprehensively synthesize evidence from RCTs, case-control studies, and cohort studies examining the impact of various pre-pregnancy lifestyle components (diet and/or physical activity) on GDM risk.

The researchers conducted a thorough literature review to assess the existing evidence on the link between pre-pregnancy lifestyle (diet and physical activity) and the risk of developing GDM. They examined previous studies that investigated lifestyle interventions during pregnancy, noting mixed results. Studies that implemented interventions early in gestation showed promising outcomes, however pre-conceptional strategies were considered to provide a more complete preventative measure. The reviewed studies identified gaps in the existing literature, including a lack of large-scale, high-quality RCTs, and particularly the underrepresentation of LMICs which experience the largest burden of GDM. This systematic review aimed to address these gaps by comprehensively summarizing the available evidence and quantifying the effect of pre-pregnancy lifestyle components.

This systematic review and meta-analysis followed a rigorous methodology. Databases (MEDLINE, Web of Science, Embase, Cochrane Central Register of Controlled Trials) were searched for studies published up to July 2022, using specific keywords related to pre-pregnancy lifestyle, interventions, and GDM. Inclusion criteria specified RCTs, cohort studies, and case-control studies evaluating the effect of pre-pregnancy lifestyle (diet and/or physical activity) on GDM prevention. Exclusion criteria included studies on women with pre-existing diabetes, women outside the 18–50 age range, and those with specific medical conditions. Two reviewers independently screened studies, using Rayyan for management. Data extraction included author, year, intervention type, sample size, country, BMI, age, and GDM outcomes. The Cochrane ROB-2 tool assessed RCT quality, while the Newcastle-Ottawa Scale assessed the quality of non-randomized studies. Meta-analysis using a random effects model calculated odds ratios (ORs) with 95% confidence intervals. Heterogeneity was assessed using I² statistics, publication bias using funnel plots and Egger’s tests, and sensitivity analysis using leave-one-out plots. The study protocol was registered in PROSPERO (CRD42020189574).

The initial search yielded 7935 studies; after screening, 30 studies (257,876 pregnancies) were included in the analysis. These included 5 RCTs (n=2471), 4 case-control studies (n=19,778), and 21 cohort studies (n=235,627). Meta-analysis of RCTs showed a non-significant 24% reduction in GDM risk in the intervention group (OR 0.76, 95% CI: 0.50–1.17, p=0.21). Subgroup analyses of RCTs from high-income countries (HICs) and LMICs were conducted. Meta-analysis of cohort studies revealed significant associations: women with higher pre-pregnancy physical activity were 34% less likely to develop GDM (OR 0.66, 95% CI: 0.44, 0.99, p=0.04); those with low carbohydrate/low sugar diets showed a 24% lower risk (OR 0.86, 95% CI: 0.68–1.09, p=0.22); and higher quality diet scores were associated with a 28% decreased risk (OR 0.72, 95% CI: 0.60–0.87, p=0.0006). Most studies (24/30) were from HICs. Funnel plots suggested low risk of publication bias, and sensitivity analysis confirmed the robustness of the results. There was significant heterogeneity across studies which likely stems from different lifestyle factors being examined. Meta-analysis of case-control studies was deemed inappropriate due to heterogeneity and overlapping study populations.

This systematic review and meta-analysis is the first to comprehensively examine the association between pre-pregnancy lifestyle and GDM risk, incorporating various dietary and physical activity components. While RCTs demonstrated a non-significant trend toward reduced GDM risk with pre-pregnancy lifestyle interventions, cohort study findings provided stronger evidence supporting the benefits of specific lifestyle factors such as increased physical activity, consumption of low-carbohydrate/low-sugar diets, and a higher quality diet. These findings align with previous research suggesting that lifestyle interventions can reduce GDM risk during pregnancy. The limited number of RCTs, particularly from LMICs, highlights a critical gap in the literature. This suggests that while pre-pregnancy lifestyle modification appears beneficial, more robust RCTs are needed to confirm these findings and ensure generalizability across diverse populations, and also to define the optimal components and delivery mechanisms for such interventions.

This study highlights the potential of pre-pregnancy lifestyle modifications in reducing GDM risk. Specific components like physical activity, low carbohydrate/low sugar diets, and high-quality diets demonstrated a positive association with GDM prevention. However, the limited number of RCTs, especially in LMICs, underscores the urgent need for further research with larger, well-designed trials that explore diverse populations and personalize interventions to improve efficacy and cost-effectiveness. Future studies should utilize objective measures and address sedentary behavior.

The study acknowledges limitations, including high heterogeneity among included studies due to the variability in lifestyle factors examined, and reliance on self-reported data via food frequency questionnaires and physical activity assessments, which may introduce recall bias. The underrepresentation of studies from LMICs, where the GDM burden is highest, limits the generalizability of the findings to these populations. Future studies should incorporate objective measures and focus on interventions that target diverse populations and address sedentary behavior.