Bone Mineral Content at Birth is Determined Both by Birth Weight and Fetal Growth Pattern

Adult peak bone mass is related to birth weight, suggesting it could be affected by fetal growth pattern. Small-for-gestational-age (SGA) newborns have lower bone mineral content (BMC), but what about adapted-for-gestational-age (AGA) newborns with fetal growth restriction? The purpose of the study was to determine the respective role of birth weight and fetal growth pattern on BMC. Full-term newborns from SGA high-risk pregnancies were included (n = 185). Estimated fetal weight percentiles were measured monthly from mid-gestation to birth, and restricted fetal growth (FGR) was defined as a loss by more than 20 percentiles. BMC was measured at birth, using dual x-ray absorptiometry. Newborns were SGA (n = 56) or AGA (n = 129). Newborns with FGR (n = 111) were AGA (n = 71) or SGA (n = 41). BMC was significantly lower in SGA than AGA (1.48 +/- 0.02 vs. 1.87 +/- 0.04 g/cm) and lower when FGR irrespective of birth weight (1.66 g/cm +/- 0.03 vs. 1.89 g +/- 0.05). In multivariate analysis, FGR and SGA were significant and independent predictors of low BMC. In conclusion, fetal growth pattern affects BMC not only in SGA infants but also when birth weight is maintained in the normal range.