Abstract
ABSTRACTAt birth, the neonatal skeleton contains 20 to 30 g calcium (Ca). It is hypothesized maternal bone mineral may be mobilized to support fetal skeletal development, although evidence of pregnancy‐induced mineral mobilization is limited. We recruited healthy pregnant (n = 53) and non‐pregnant non‐lactating (NPNL; n = 37) women aged 30 to 45 years (mean age 35.4 ± 3.8 years) and obtained peripheral quantitative computed tomography (pQCT) and high‐resolution pQCT (HR‐pQCT) scans from the tibia and radius at 14 to 16 and 34 to 36 weeks of pregnancy, with a similar scan interval for NPNL. Multiple linear regression models were used to assess group differences in change between baseline and follow‐up; differences are expressed as standard deviation scores (SDS) ± SEM. Decreases in volumetric bone mineral density (vBMD) outcomes were found in both groups; however, pregnancy‐related decreases for pQCT total and trabecular vBMD were −0.65 ± 0.22 SDS and −0.50 ± 0.23 SDS greater (p < .05). HR‐pQCT total and cortical vBMD decreased compared with NPNL by −0.49 ± 0.24 SDS and −0.67 ± 0.23 SDS, respectively; trabecular vBMD decreased in both groups to a similar magnitude. Pregnancy‐related changes in bone microarchitecture significantly exceeded NPNL change for trabecular number (0.47 ± 0.23 SDS), trabecular separation (−0.54 ± 0.24 SDS), cortical thickness (−1.01 ± 0.21 SDS), and cortical perimeter (0.78 ± 0.23 SDS). At the proximal radius, cortical vBMD and endosteal circumference increased by 0.50 ± 0.23 SDS and 0.46 ± 0.23 SDS, respectively, compared with NPNL, whereas cortical thickness decreased −0.50 ± 0.22 SDS. Pregnancy‐related decreases in total and compartment‐specific vBMD exceed age‐related change at the distal tibia. Changes at the radius were only evident with pQCT at the cortical‐rich proximal site and suggest endosteal resorption. Although the magnitude of these pregnancy‐related changes in the appendicular skeleton are small, if they reflect global changes across the skeleton at large, they may contribute substantially to the Ca requirements of the fetus. © 2020 Crown copyright. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). This article is published with the permission of the Controller of HMSO and the Queen's Printer for Scotland.
Highlights
R eproduction places increased pressure on maternal mineral economy to supply essential nutrients during pregnancy
Women with a singleton pregnancy achieved by natural conception and aged 30 to 45 years were recruited between March 2017 and December 2018 at the Rosie Hospital Cambridge University Hospitals (CUH), Cambridge, UK
This study presents novel evidence of compartment-specific changes in maternal bone mineral density, microarchitecture, geometry, and distribution during pregnancy in women aged 30 to 45 years old
Summary
R eproduction places increased pressure on maternal mineral economy to supply essential nutrients during pregnancy. The few studies that have used X-ray-based techniques to explore pregnancy-related skeletal changes have typically either obtained dual-energy X-ray absorptiometry (DXA) scans pre-pregnancy and postpartum or scanned the forearm with DXA during pregnancy to quantify the changes in areal bone mineral density (aBMD) Both these approaches have limitations because comparing pre-pregnancy and postpartum scans are confounded by the initiation of lactation, and forearm DXA cannot distinguish between cortical and trabecular bone. To date, only two studies in pregnancy have been published using single-slice pQCT[37,38] and none using HR-pQCT
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