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/m3 to 26.2 kg/m3 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.