Radiofrequency Echographic Multi-Spectrometry (REMS) for Bilateral Femoral Neck Assessment in Pregnant Women: A Cross-Sectional Study

Pregnancy is associated with physiological adaptations in calcium metabolism and skeletal homeostasis that may result in temporary reductions in bone mineral density (BMD). However, routine skeletal assessment during pregnancy remains limited because dual-energy X-ray absorptiometry (DXA) involves ionizing radiation. This study aimed to compare bilateral femoral neck BMD and Z-scores in pregnant and non-pregnant women using Radiofrequency Echographic Multi-Spectrometry (REMS), a radiation-free ultrasound-based technology, and to assess correlation between bilateral measurements. In this cross-sectional study, 100 women were enrolled, including 40 pregnant women and 60 non-pregnant women with comparable age and body mass index (BMI). Bilateral femoral neck BMD and age-adjusted Z-scores were evaluated using REMS. Pregnant women had a mean age of 33 ± 5 years, pre-pregnancy BMI of 25.8 ± 6.5 kg/m2, and gestational age of 21 ± 5 weeks, with no significant differences in age or pre-pregnancy BMI compared with controls. Pregnant women demonstrated significantly lower left femoral neck BMD than controls (0.805 vs. 0.862 g/cm2; p = 0.0018) and lower left femoral neck Z-scores (−0.08 vs. 1.18 SD; p = 0.003). A strong positive correlation between left and right femoral neck BMD was observed (R = 0.78). Similarly, right femoral neck BMD was significantly lower in pregnant women compared with controls (0.835 g/cm2 vs. 0.892 g/cm2; p = 0.0026). The right femoral neck Z-score was 0.15 ± 1.15 SD in pregnant women and 1.45 ± 1.10 SD in controls (p = 0.002). REMS demonstrated the ability to detect differences in femoral neck bone parameters between pregnant and non-pregnant women while providing bilateral measurement consistency. These findings support the feasibility of REMS as a safe, radiation-free approach for assessing maternal skeletal status during pregnancy. However, the cross-sectional design and lack of longitudinal follow-up limit conclusions regarding the progression and reversibility of pregnancy-associated bone changes. Future prospective studies with larger cohorts and postpartum monitoring are needed to further define the clinical role of REMS in maternal bone health assessment.