Bone Mineral Density as Measured by Calcaneal Quantitative Ultrasound (QUS) Among First and Third Trimester Egyptian Pregnant Women "A Pilot Study"

Abstract

Pregnancy defines a challenging period to the mother’s bones because the building of the fetal skeleton requires a substantial transfer of calcium. This process is particularly intense during the third trimester, when fetal bones experience substantial growth and calcification. The regulatory mechanisms are still poorly understood, but it seems patent that the drainage of calcium from the mother has to bear some level of deterioration of the maternal skeleton unless compensatory mechanisms of enough potency exist. If an adequate balance is not achieved, pregnancy would define a vulnerability period from maternal bones. Osteoporosis or even fragility fractures might be conceived whether the decalcifying process is particularly intense or whether there is an osteopenic background. In fact, isolated cases of osteoporosis or fragility fractures have been described before, however the process has to be transitory, because pregnancy has not been detected as a risk factor for postmenopausal osteoporosis (Smith R. et al., 2011). Various methods to assess the changes in bone mineral density (BMD) during pregnancy have been studied. The use of standard dual-energy X-ray absorptiometry (DXA) in pregnant women has been limited by the potential harmful effects of radiation during pregnancy. Studies that utilize this method for assessments would obtain measurement in women before pregnancy and then repeat it in the early postpartum period, yet the actual changes during pregnancy could not be assessed. The recent development in quantitative ultrasound methods for assessment of BMD in pregnancy carries the particular advantage of being free from irradiation effects (Pluskiewicz W. et al., 2004). Ultrasonography (USG) measurements have been found to correlate well with BMD measurements compared to conventional DXA methods in non-pregnant subjects, and could be used alone for prediction of fracture risks in postmenopausal women. Ultrasound measurements may be performed at different sites, including the tibia, os-calcis, metacarpals and phalanges. (Pluskiewicz W. et al., 2004). Serial USG measurements across advancing gestations in pregnancy have been able to show consistent progressive BMD loss in different bone sites.The degree of BMD changes during pregnancy has been correlated with higher bone turnover as indicated by biochemical markers, as well as with maternal characteristics such as low initial BMD in early pregnancy and high body fat accumulation during pregnancy. It could also be related to calcium intake and mechanical