Higher maternal dietary protein intake in late pregnancy is associated with a lower infant ponderal index at birth

Aim: A high ponderal index at birth has been associated with later obesity and it has been suggested that intervention to prevent obesity and its sequela should consider the antenatal period. In this context, we investigated the association between maternal nutrition and birth anthropometry.

Design: We analyzed data on 1040 mother-infant pairs collected during the Tasmanian Infant Health Survey (TIHS), Tasmania, 1988-1989. Maternal dietary intake during pregnancy was measured by food frequency questionnaire (FFQ) applied soon after birth. Outcomes of interest were birth weight, birth length, head circumference, ponderal index, head circumference -to-ponderal index ratio, placenta-to-birth weight ratio and head circumference-to-birth length index.

Results: In multiple regression model, an increase of 10 g of absolute protein intake/day was associated with a reduction in birth weight of 17.8 g (95% CI: -32.7, -3.0; P = 0.02). Protein intake was also associated negatively with ponderal index (β = 0.01; 95% CI: -0.02, -0.00; P = 0.01). A 1% increase in carbohydrate intake resulted in a 1% decline in placental weight relative to birth weight. Higher protein intake in the third trimester was associated with a reduced ponderal index among large birth weight infants but not low birth weight infants.

Conclusions: This raises the possibility that any effect of high protein in altering infant anthropometry at birth may involve changes in body composition and future work to examine how a high-protein diet influences body composition at birth is warranted.