D. Holmberg-marttila et al., Changes in bone mineral density during pregnancy and postpartum: Prospective data on five women, OSTEOPOR IN, 10(1), 1999, pp. 41-46
Areal bone mineral density (BMD, g/cm(2)) of five healthy women (aged 26-30
years) was measured at the lumbar spine, right femoral neck and dominant d
istal radius with dual-energy X-ray absorptiometry before pregnancy, immedi
ately after delivery, 1 month after the resumption of menses and 1 year the
reafter. Because of the small number of subjects, only individual changes i
n BMD that were greater than 2(root)2 times the short-term in vivo precisio
n were considered as significant changes. To obtain a further perspective,
the reproduction-related BMD changes were compared with twice the standard
deviation (SD) of the BMD changes in healthy premenopausal women (about +/-
5%), and with the SD of the BMD in a cross-sectional sample of young health
y women. The duration of postpartum amenorrhea (PPA) and of lactation in ou
r subjects ranged from about 2 months to 1 year and from 5 months to almost
2 years, respectively, No clear association between PPA and lactation coul
d be seen. The magnitudes of reproduction-related BMD changes in general se
emed not to differ substantially from about +/-5% variability in BMD change
s in healthy nonpregnant and nonlactating women. There was, however, some t
endency toward systematic bone loss at the lumbar spine (about -3%) during
pregnancy and at the femoral neck during PPA (about -5% as compared with pr
epregnancy data). Some individuals can yet show large, systematic bone loss
es comparable to 1 SD in magnitude. The site-specific reproduction-induced
bone loss and consequent recovery are apparently multifactorial phenomena t
hat may be related not only to duration and magnitude of lactation and/or d
uration of postpartum amenorrhea, but also to prevailing biomechanical and
dietary factors, and other yet unknown individually modulated factors.