The impact of quality of diet and other factors on birth weight of infants.

Quality of the mother's diet, expressed as a NAR index, was significantly correlated (r = 0.301, P less than 0.05) with birth weight of the infant. Eight women who reported that they had smoked during pregnancy had infants with significantly lower birth weights (P less than 0.01), gained less weight during prenatal care (P less than 0.01), and had a lower NAR index (P less than 0.10) than 32 women who said they did not smoke during pregnancy. The relationship of birth weight to 44 maternal and environmental factors was examined by multiple regression analysis to isolate variables significantly and independently related to birth weight. This analysis showed that birth weight of the infant was positively related to number of weeks of gestation, overall dietary quality, delivery weight of the mother squared, age of the mother squared, and number of previous pregnancies squared, and negatively related to weeks of gestation squared, iron and protein intake, age of mother, number of people in the household, and number of cigarettes smoked by the mother per day. Nine factors accounted for up to 86% of the variability in birth weight. Inclusion of quality of the diet improved the prediction equations by 6 to 8%.