Effects of a low-glycemic index diet during pregnancy on offspring growth, body composition, and vascular health: a pilot randomized controlled trial.

Background: Elevated maternal blood glucose concentrations may contribute to macrosomia, adiposity, and poorer vascular health in the offspring.

Objective: The aim was to explore the effect of a low-glycemic index (low-GI) diet during pregnancy on offspring growth, adiposity, and arterial wall thickness during infancy.

Design: This was a longitudinal follow-up study in a self-selected subgroup of mother-infant pairs (n= 59) participating in a larger randomized trial comparing the effects on perinatal outcomes of a low-GI diet and a conventional high-fiber (HF) diet during pregnancy. Infant anthropometric measurements were taken every month for 6 mo and then at 9 and 12 mo of age. Adiposity was assessed at birth and at 3 mo by air-displacement plethysmography by using the Pea Pod system (Cosmed) and at 6 and 12 mo by bioimpedance analysis (Bodystat). Aortic intima-media thickness was assessed at 12 mo by high-resolution ultrasound (Philips).

Results: Maternal dietary GI was lower in the low-GI group than in the HF group (51 ± 1 compared with 57 ± 1;P< 0.001). No differences in neonatal outcomes were observed in the main trial. In the self-selected subsample, birth weight and length z scores were lower in the low-GI group than in the HF group (birth weight z score: 0.2 ± 0.2 compared with 0.7 ± 0.2, respectively;P= 0.04; birth length z score: 0.3 ± 0.2 compared with 0.9 ± 0.2, respectively;P= 0.04), but adiposity from birth to 12 mo of age and growth trajectories from 1 to 12 mo of age were similar. Aortic intima-media thickness was lower in the low-GI group than in the HF group (657 ±12 compared with 696 ± 12 μm, respectively;P= 0.02), which was partly mediated by differences in birth weight.

Conclusion: In women at risk of gestational diabetes mellitus, a low-GI diet influences offspring birth weight, birth length, and arterial wall thickness in early childhood, but not adiposity or growth trajectory during the first year of life. This trial was registered at anzctr.org.au as ACTRN12610000681055.