Maternal Bone Mineral Density Changes during Pregnancy: A Longitudinal Prospective Study Using Radiofrequency Echographic Multi-Spectrometry.

Introduction: The contribution of bone resorption to fetal calcium demand during pregnancy is still unclear due to the methods used to study bone turnover. Recently, bone mineral density (BMD) was measured in the third trimester of pregnancy using radiofrequency echographic multi-spectrometry (REMS) technology, a nonionizing technique. Thus, the present study aimed to determine changes in maternal BMD during pregnancy in healthy women using REMS. Methods: A prospective cohort study was conducted among 164 pregnant women. Femoral neck BMD was determined in all patients once in each trimester by REMS densitometry. Lifestyle and demographic data were collected by interview. Previous reports in postmenopausal women identified two subpopulations based on the annual rate of bone loss; thus, the bone loss group was stratified into slow and fast bone loser groups. Results: BMD was significantly lower in the second and third trimesters compared with the first trimester. A wide interindividual variation in BMD change was observed; therefore, women were stratified into two groups: bone loss (n = 136) and bone gain (n = 28) according to the rate of BMD loss or gain from the first to third trimester. Binary logistic regression revealed that no calcium + vitamin D and no multivitamin intake were independent factors significantly associated with bone loss at the end of pregnancy. Fisher's exact test revealed a significant association between gravidity and fast bone loss. Conclusions: Decreased BMD during pregnancy is associated with no multivitamin intake and no calcium + vitamin D intake. In addition, fast bone loss is associated with the number of pregnancies.