Can physical activity and dietary interventions improve maternal and fetal outcomes in women with gestational diabetes mellitus? A systematic review and meta-analysis

Objective. To assess the effect of increasing physical activity or modifying diet on maternal and fetal outcomes for women with gestational diabetes mellitus. Methods. Five electronic databases and Google Scholar were searched to identify randomised controlled trials (RCTs) of physical activity or diet interventions, published before August 2017. Interventions were included if participants had gestational diabetes, there was a control/comparison group and at least one outcome of interest was reported: insulin use, caesarean section or birth weight. Findings. Twenty-one studies (1613 participants) were included in the systematic review, 14 were diet and seven were physical activity interventions. Diet types included low glycaemic, energy restricted and dietary approaches to stop hypertension (DASH). Physical activity included brisk walking, resistance training and home-based cycling. Meta-analysis of 17/21 RCTs suggested physical activity reduced insulin use by 47% (OR 0.53, 95% CI 0.29,0.97, P=0.04) and the DASH diet reduced insulin use by 89% (OR 0.11, (95% CI 0.04, 0.29, P<0.00001). Neither physical activity or combined diet interventions reduced the number of caesarean sections and only the diet interventions reduced birth weight -289.80g (95% CI -526.87, -52.72, I2=98%). The DASH intervention produced statistically significant results across all three outcomes. In the meta-analysis, 15/17 studies scored a highrisk of bias on at least one domain. Conclusions. Physical activity interventions can reduce insulin use and diet interventions can reduce birth weight in women with gestational diabetes. Further intervention studies are needed that are theoretically underpinned and provide social support as these elements were lacking in the included studies.