Bone in the pregnant mother and newborn at birth

Abstract

Background: Changes in maternal bone during pregnancy may affect fetal bone mineralization.

Issues: The biphasic changes in maternal bone histology (temporary loss of cancellous bone in early pregnancy restored by term gestation) are consistent with corresponding blood biochemistry changes; increased bone resorption markers in the first trimester, while bone formation markers increased in the last trimester. Postpartum bone mineral density (BMD) by DEXA is increased at cortical bone and decreased at trabecular bone sites compared with prepregnancy values. The mean reduction of spine BMD is 3.5% from prepregnancy to immediate postpartum. Neonatal bone mineral content (BMC) is different by season of birth, low weight relative to gestation, and having a diabetic mother. Lower total body BMC and high bone resorption marker in winter vs. summer-born newborns was related to low vitamin D, indicating alterations of fetal bone metabolism by maternal D deficiency. Lower BMC and decreased bone formation marker in infants born small for gestational age than those born appropriate for gestation may relate to reduced transplacental mineral transfer. Low BMC in infants of diabetic mother was correlated inversely with poor control of maternal diabetes during early pregnancy.

Conclusions: During pregnancy, maternal bone mineral metabolism are changed, and influences on fetal bone mineralization occur in utero.