Body mass index, prebiotic supplementation during pregnancy and gestational diabetes mellitus risk: an effect modification analysis from a randomised controlled trial.

BACKGROUND

Prebiotic dietary supplementation has been shown to improve glucose homeostasis in type 2 diabetes patients. The aim of this analysis was to determine whether pre-pregnancy body mass index (BMI) modifies the effect of prebiotic supplementation from mid-pregnancy on reducing the risk of gestational diabetes mellitus (GDM).

METHODS

In a double-blinded, randomised controlled trial, pregnant women < 21 gestational weeks were randomly assigned (1:1) to consume daily prebiotics (14.2 g galacto-oligosaccharides and fructo-oligosaccharides) or placebo (8.7 g maltodextrin) powder. An effect modification analysis was performed to assess the heterogeneity of the effect of prebiotic supplementation in relation to pre-pregnancy BMI on GDM diagnosis.

RESULTS

Between June 2016 and November 2021, 329 women were assigned to the prebiotic group (50.4%), and 323 (49.5%) were assigned to the placebo group. Overall, 288 of 652 women (44.2%) were classified as overweight/obese prior to pregnancy (BMI ≥ 25 kg/m2). The distribution was balanced, with 146/329 (44.4%) randomised to the prebiotics group and 142/323 (44.0%) in the placebo group. Pre-pregnancy BMI modified the effect of prebiotic supplementation, with the intervention reducing GDM rates in women with a BMI ≥ 25 kg/m2 (prebiotic group 11.0% vs. control group 21.8%; adjusted relative risk 0.50; 95% confidence interval (CI) 0.28 to 0.89) but not in women with a pre-pregnancy BMI < 25 kg/m2 (7.7–7% vs. 4.4%; adjusted relative risk 1.72; 95% CI 0.70 to 4.19; interaction p = 0.02).

CONCLUSION

Pre-pregnancy BMI was found to modify the effect of prebiotic supplementation on GDM rates, with benefits observed in overweight and obese women. Our results highlight a target population for future randomised controlled trials to further investigate the effects of prebiotic supplementation during pregnancy on reducing the risk of GDM.  TRIAL REGISTRATION: Primary and secondary infant allergic disease outcomes of this randomised controlled trial have been previously published. The trial was registered with the Australian New Zealand Clinical Trial Registry: ACTRN12615001075572, https://www.anzctr.org.au/on13/10/2015 .