Changes in bone mineral density of the os calcis as measured by quantitative ultrasound during pregnancy and 24 months after delivery

Aim: To evaluate the use of quantitative ultrasound measurement of the os calcis to monitor bone mineral density (BMD) changes in pregnancy and 24 months after delivery. Methods: Low-risk patients booked before 20 weeks of gestation were recruited prospectively over a period of 12 months. BMD measurements of the os calcis were taken using quantitative ultrasound between 14 and 20 weeks and after 36 weeks using the Hologic Sahara system. Body weight and fat composition were also measured at each occasion. The measurements were repeated 24-28 months after the index delivery. Those who were delivered preterm or those diagnosed to have significant medical or antenatal complications were excluded. Results: A total of 95 patients completed the study, of which 55 (57.8%) were primiparous and 40 (42%) were multiparous. A mean fall in BMD of 0.0389 g/cm(2) was demonstrable from early to late gestation. The mean BMD difference between the 2-year assessment and early pregnancy (Delta BMD) was) -0.008 g/cm(2). D BMD was negligible for multiparous women compared to a small loss in primiparous women (0.0006 vs) -0014 g/cm(2), P = 0.026). There were no significant differences in Delta BMD between those who lactated for over 16 weeks (n = 35) and those who did not (n = 60). A logistic regression model showed that the extent of BMD loss during pregnancy and pregnancy weight gain were significant factors associated with BMD changes 24 months after delivery. Conclusion: Bone mineral density loss during pregnancy that was detectable by quantitative ultrasound at the os calcis has largely recovered at 24 months after delivery.