Changes in bone mass as determined by ultrasound and biochemical markers of bone turnover during pregnancy and puerperium: a longitudinal study.

In a longitudinal study, we analyzed the speed of sound (SOS) and broadband ultrasound attenuation (BUA) of the os calcis as an index of bone mineral density (BMD) to define the effects of pregnancy and lactation on bone metabolism. We used an ultrasound bone densitometer and measured 6 biochemical markers of bone turnover in 18 healthy women throughout pregnancy and puerperium. The measurement of SOS and BUA by such an ultrasound device was clinically advantageous; not only is it radiation-free technology, but it also correlates highly with BMD measured by conventional X-ray bone densitometry. While a significant decrease in SOS was found in the 3rd trimester of pregnancy as compared with the early stage of pregnancy, there was no difference in both SOS and BUA between the breast-feeding women and the principally formula-feeding women during a 6-month period of puerperium. The analysis of biochemical markers revealed that both bone formation and bone resorption were elevated in the 3rd trimester of pregnancy as well as during puerperium, and that the breast-feeding women had significantly higher bone metabolism than the principally formula-feeding women. These results indicate that bone mass decreases as bone turnover itself is enhanced during pregnancy, while lactation does not substantially affect bone mass during at least 6 months of puerperium, although bone turnover is active.