Maternal birthweight and diet in pregnancy in relation to the infant's thinness at birth

Objective To examine how maternal diet in pregnancy and parental body size and birthweight influence an infant's thinness at birth measured by a low ponderal index. Design An observational study of newborn infants and their parents. Setting Southampton, England. Population Five hundred and thirty-eight infants born at term. Main outcome measure Ponderal index at birth. Results Women who had a high intake of carbohydrate in early pregnancy and a low intake of dairy protein in late pregnancy tended to have infants that were thin at birth (P = 0.01 and P = 0.03, respectively, in a simultaneous analysis). Women who themselves had a low birthweight also tended to have thin infants, ponderal index falling from 28.3 kg/m(3) to 26.2 kg/m(3) as the women's birthweights decreased from more than 4.0 kg to 2.5 kg or less (P < 0.0001). Tall fathers had thin infants, but ponderal index was not related to the women's heights or the fathers' birthweights. Conclusion These associations may reflect constraints on placental development imposed by a woman's nutrition in pregnancy and during her own intrauterine life. Effects of the father's height may be mediated through genetic influences on skeletal growth.