Neonatal bone mass: Influence of parental birthweight, maternal smoking, body composition, and activity during pregnancy

Evidence is accumulating that intrauterine growth and development may influ ence an individual's risk of osteoporosis in later adult life. To examine m aternal and paternal influences on intrauterine skeletal growth, we used du al-energy X-ray absorptiometry to measure the neonatal bone mineral content (BMC) and bone mineral density (BMD) of 145 infants born at term. Independ ently of the infant's duration of gestation at birth, the birthweights of b oth parents and the height of the father were positively correlated with ne onatal whole body BMC. Women who smoked during pregnancy had infants with a lower whole body BMC and BMD; overall, there was a 7.1-g (11%) average dif ference between whole body BMC of infants whose mothers did and did not smo ke during pregnancy (p = 0.005). Women with thinner triceps skinfold thickn esses (reflecting lower fat stores) and those who reported a faster walking pace and more frequent vigorous activity in late pregnancy also tended to have infants with a lower BMC and BMI) (p values for BMC; 0.02, 0.03, and 0 .05, respectively). Maternal thinness and faster walking pace but not mater nal smoking or parental birthweight also were associated with lower bone mi neral apparent density (BMAD). The influences on skeletal growth and minera lization were independent of placental weight, a marker of the placental ca pacity to deliver nutrients to the fetus. These observations point to a com bination of genetic and intrauterine environmental influences on prenatal s keletal development and suggest that environmental modulation, even at this early stage of life, may reduce the risk of osteoporosis in adulthood.