Effect of Chronic Maternal Calcium (Ca) Supplementation on Fetal Bone Mineralization (FBM). † 1535

Pregnancy is a time of physiologic stress on Ca homeostasis but there has been no systematic study on the effect of maternal Ca intake on FBM. We tested the hypothesis that maternal Ca supplementation increases FBM as indicated by dual energy X-ray absorptiometry (DXA) measurements of the neonate. Two hundred eighty-nine women enrolled in a randomized trial of Ca supplementation during pregnancy were approached to participate in a study of FBM; 276 agreed. The women had been randomized to receive 2-g elemental Ca or placebo tablets daily from 13-21 wks gestation until delivery. At each prenatal visit compliance was determined by pill counts. The treatment grp received an average of 1284 mg supplemental Ca/d. All mothers were provided with the same prenatal vitamin supplement. There were no significant differences in maternal dietary Ca, protein and energy intake between grps based on the average of 24-hr recalls conducted at randomization and at 32-33 wks gestation. There was also no significant difference between grps in maternal body mass index and wt gain during pregnancy. Eight neonates were not studied because of 2 deaths, 5 technical problems with DXA and learly discharge. Twelve infants had delayed DXA studies beyond one week after birth because of illness. Of the remaining 256 infants (128/grp), DXA measurements were performed by the same operator at 1.75 (mean) ± 0.1 (SEM) d. Scan acquisition used Hologic 1000/W densitometer (Hologic Inc., Waltham, MA) and infant platform. Quality control scans using manufacturer supplied phantom showed a long term (>3 yrs) CV of<0.5%. Only scans without movement artifact were analyzed using software(v5.64 for total body and v4.57Q for spine) developed in conjunction with the manufacturer. General linear modeling showed that the mean total body bone mineral content (BMC) and lumbar spine BMC were significantly (p<0.05) higher in the treatment grp (13.4% and 14.6%, respectively) at the lowest quintile of maternal dietary Ca intake (mean 504 [treatment] vs 555 [placebo] mg/d). The effect of Ca supplementation on FBM was not significantly different at the highest quintile of dietary Ca intake. We conclude that FBM can be significantly improved by Ca supplementation at low maternal dietary Ca intake.