The relationship between maternal dietary intake and infant birthweight

Zinc and folate are important for fetal growth. However, the relationship between the dietary intake of these nutrients and pregnancy outcome is not settled.

A prospective study was conducted to ascertain the relationship between maternal dietary zinc and folate intake (n = 1398), serum zinc and folate levels (n = 289), and infant birthweight. Twenty-four hour recalls were used to measure energy, zinc, folate and other nutrient intakes at 18 and 30 weeks of gestation. Subjects in the study were offered daily folic acid (1.0 mg) and iron (60 mg as ferrous sulfate) at enrollment.

Maternal zinc nutriture as assessed by serum and dietary intake was not associated with birthweight or length of gestation. There was a small but significant positive association between maternal folate intake and adjusted infant birthweight (beta = 0.05, p = 0.03). The indirect measures of maternal nutritional status including maternal pre-pregnancy weight (beta = 8.0, p = 0.0001) and weight gain during pregnancy (beta = 18.1, p = 0.0001) were stronger predictors of adjusted infant birthweight as compared to energy intake and intake of zinc and folate. An increase of 320, 290, and 48 g in infant birthweight was associated with the 90th-10th percentile difference for pre-pregnancy weight, weight gain during pregnancy, and folate intake respectively.

These results indicate that pre-pregnancy weight and weight gain during pregnancy are both strong predictors of infant birthweight. Folate intake, although significantly associated with birthweight, was a weak predictor while maternal intake of zinc and other nutrients was not associated with birthweight.