Pregnancy-associated Changes in Bone Density and Bone Turnover

Re: Fiore CE, Pennisi P, DiStefano A, Riccobene S, Caschetto S. Pregnancy-associated changes in bone density and bone turnover in the physiological state: prospective data on sixteen women. Horm Metab Res 2003; 35: 313 - 318.

An interesting study on skeletal status in pregnancy was recently published by Fiore et al. [1]. Longitudinal measurements were performed on 16 women. Total-body, spine and hip BMD values were established before pregnancy and after delivery. Additional measurements included quantitative ultrasound QUS at the calcaneus collected at baseline and in the first, second and third trimesters. The authors obtained significant decreases for BMD variables ranging from 7.8 % for femoral neck to 13.4 % for total body. These values exceeded those adequate results usually given by other authors. The QUS data provided a contrasting view; broadband ultrasound attenuation was stable from baseline to third trimester, after which a significant decrease of 14 % was observed. This is a very uncommon observation since the period between measurement in last trimester and postpartum only lasted 6 weeks. One possible explanation may be an influence of lactation since the last measurement was performed 2 weeks after delivery. The authors, however, did not state whether the infants were breast-fed. This information seems to be especially important, as it is well known that decreases in bone status observed during lactation are even greater than during pregnancy. The authors stated in the discussion that ”our data would confirm the general issue that considerable component of bone loss observed postpartum is due to the pregnancy itself”. This opinion is not fully confirmed by study results; BMD was not established (for obvious ethics reasons) during pregnancy, so it cannot be excluded that the pattern of change in BMD was similar to those shown by QUS, as the average mean drop in BMD values was about 10 %, and this is comparable to the decrease in BUA (14 %). The average significant decrease does not mean that skeletal variables studied were decreased in all women. In order to explain these study results, I would suggest that the authors present their results for the individual subjects. Additional analysis using individual changes in skeletal variables corrected using the least-significant-change method referring to the changes in biochemical markers in individual women should have been performed. In my opinion, this analysis might give additional clinically important information on skeletal and metabolic changes during pregnancy, helping to explain the results of the study.

References

• 1 Fiore C E, Pennisi P, DiStefano A, Riccobene S, Caschetto S. Pregnancy-associated changes in bone density and bone turnover in the physiological state: prospective data on sixteen women.  Horm Metab Res. 2003;  35 313-318