Predictors of birthweight in women at high risk of gestational diabetes mellitus (#6)
The prevalence of both obesity and gestational diabetes mellitus (GDM) is rising. These conditions are associated with adverse pregnancy outcomes including fetal overgrowth and increased risk of metabolic disease in the offspring. Our aim was to investigate the effect of a low glycemic index (GI) versus a conventional high fibre (HF) diet on pregnancy outcomes and neonatal body composition in women at high risk of developing GDM.
139 women (mean ± SD age: 34.7±0.4 y; pre-pregnancy BMI: 25.3±0.5 kg/m2) at high risk of GDM (age ≥ 35 yr, family history of type 2 diabetes, ethnicity, previous GDM or BMI≥30 kg/m2) were randomized to follow a low GI (LGI, n=72; target GI ≈ 50) or a high fiber, moderate GI diet (HF, n=67; target GI ≈ 60). Women were enrolled at 14-20 weeks gestation (mean 18 weeks). Dietary intake was assessed by 3-day food records at study entry. Neonatal body composition was measured by air displacement plethysmography using PeaPod®. Pregnancy outcomes were collected from medical records.
The dietary intervention did not result in any differences in birth weight (LGI 3270±50 vs HF 3260±60 g, p = 0.906), ponderal index (LGI 2.71±0.03 vs HF 2.69±0.03 kg/m3, p=0.958), birth weight centile (LGI 46.2±3.2 vs HF 42.8±3.3, p=0.888), %fat (LGI 10±1 vs HF 10±1%, p = 0.347), or adverse pregnancy outcomes. However, increased maternal BMI (p=0.02), mode of delivery (p=0.01) and mother’s dietary GI at baseline (p=0.035) were predictors of a higher birth weight z-score.
In intensively monitored women at high risk of GDM, a low GI diet and a conventional high fibre diet produced similar pregnancy outcomes. However, maternal BMI and a high GI diet in early pregnancy appear to increase birth weight. These findings suggest that interventions to improve pregnancy outcomes need to begin prior to conception.