title: Lumbar bone mineral density changes during pregnancy and lactation.
abstract: OBJECTIVE
  To elucidate the change of bone metabolism in the lumbar trabecular and its relationship with serum hormonal changes in pregnancy and lactation.
  
  
  METHODS
  In a cross-sectional study, we measured the bone mineral density (BMD) of 2-4 lumbar vertebrae of 571 puerperae at days 3-5 postpartum and 341 healthy, non-pregnant women (control subjects) of approximately the same age by dual energy X-ray absorptiometry. In a longitudinal study, we also measured the BMD of 111 puerperae at 3 and 6 months after delivery.
  
  
  RESULTS
  The mean BMD at days 3-5 postpartum was significantly lower than that of the control (1.013+/-0.005 vs. 1.032+/-0.006 g/cm2, P = 0.019). The lactating group showed BMD decrement to 95.1+/-0.5% (n = 69) and 94.1+/-0.7% (n = 61) at 3 and 6 months postpartum, respectively, compared with days 3-5 postpartum, and the amenorrhea group showed the same tendency. The non-lactating group and resumption of menses group did not show a BMD decrement postpartum. In the lactating group, serum estradiol was significantly lower than in the non-lactating group at 3 months postpartum, serum prolactin and bone alkaline phosphatase levels were higher than in the non-lactating group at 3 and 6 months postpartum.
  
  
  CONCLUSIONS
  Pregnancy may cause a decrease of lumbar BMD, and the lactation and amenorrhea also cause a decrease of BMD. In addition to lactation status, the ovarian dysfunction is one of the factors in bone loss during lactation.
authors.affiliation: Department of Obstetrics and Gynecology, Niigata University School of Medicine, Niigata City, Japan. akirahon@med.niigata-u.ac.jp
authors.forename: A
authors.initials: A
authors.lastname: Honda
authors.forename: T
authors.initials: T
authors.lastname: Kurabayashi
authors.forename: T
authors.initials: T
authors.lastname: Yahata
authors.forename: M
authors.initials: M
authors.lastname: Tomita
authors.forename: K
authors.initials: K
authors.lastname: Takakuwa
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D015519:Bone Density / Q000502:physiology*; D003430:Cross-Sectional Studies; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D007774:Lactation / Q000378:metabolism*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000378:metabolism; D011247:Pregnancy / Q000378:metabolism*; D011388:Prolactin / Q000097:blood