Infant growth and bone mineralization: The determination of relative effects of parental characteristics, gestational age at birth and nutrition

Fetal growth and development of bones is affected by the intrauterine environment and by the genetic potential. This study was undertaken to determine the relative effects of parental characteristics, gestational age at birth and nutrition on infant growth and bone mineralization. A secondary objective was to investigate the effects of programming in the third trimester due to preterm birth on overall growth and bone mass at term age as measured by anthropometry and bone mass. Twenty-one very preterm infants (gestational age 28.5 +/- 1.8 weeks) were compared to 21 term born infants (gestational age 39.1 +/- 1.2 weeks) for anthropometry, and bone mass at term age. Blood and urine samples were collected throughout very preterm infant hospital stay and at birth in term infants for the measurement of markers of bone metabolism. Nutrient intake of mothers and very preterm infants were assessed and a morning maternal blood sample was obtained for assessment of bone metabolism. Bone mass of parent's and infant's hip/femur, spine and whole body were assessed using dual energy x-ray absorptiometry. Very preterm infant femur, spine and whole body bone mineral content (BMC) were significantly lower than infants born at term age despite adjustment for body size. Maternal diet, parental anthropometry and parental bone mass were more predictive of preterm infant BMC than term infant BMC. These results suggest that early maternal diet and genetics strongly influence bone mass of infants born preterm and that the trajectory of bone growth is programmed early in gestation.