Pregnancy and Glycemic Index Outcomes study: effects of low glycemic index compared with conventional dietary advice on selected pregnancy outcomes1-3

Background: Eating carbohydrate foods with a high glycemic index (GI) has been postulated to result in fetoplacental overgrowth and higher infant body fat. A diet with a low glycemic index (LGI) has been shown to reduce birth percentiles and the ponderal index (PI). Objectives: We investigated whether offering LG1 dietary advice at the first antenatal visit would result in a lower fetal birth weight, birth percentile, and PI than providing healthy eating (HE) advice. This advice had to be presented within the resources of routine antenatal care. Design: The Pregnancy and Glycemic Index Outcomes study was,a 2-arm, parallel-design, randomized, controlled trial that compared the effects of LGI dietary advice with HE advice on pregnancy outcomes. Eligible volunteers who attended for routine antenatal care at <20 wk of gestation were randomly assigned to either group. Results: A total of 691 women were enrolled, and 576 women had final data considered. In the LGI group, the GI was reduced from a mean (+/- SEM) of 56 +/- 0.3 at enrollment to 52 +/- 0.3 (P < 0.001) at the final assessment. There were no significant differences in primary outcomes of fetal birth weight, birth percentile, or PI. In a multivariate regression analysis, the glycemic load was the only significant dietary predictor (P = 0.046) of primary outcomes but explained < 1% of all variation. Conclusion: A low-intensity dietary intervention with an LGI diet compared with an HE diet in pregnancy did not result in any significant differences in birth weight, fetal percentile, or PI.