title: Differences in bone metabolism between singleton pregnancy and twin pregnancy.
abstract: OBJECTIVE
  The objective of this study was to examine the influence of twin pregnancy on calcium metabolism, including bone turnover markers and calcium-regulating factors, by comparison between singleton pregnancy and twin pregnancy in women during pregnancy and puerperium in cross-sectional and longitudinal studies.
  
  
  METHODS
  Women with singleton and twin pregnancies were recruited from the outpatient clinic of Tokushima University Hospital. In both cross-sectional and longitudinal studies, bone formation and resorption markers, mineral metabolism and calcium-regulating factors were measured at 10, 25, 30 and 36 weeks of pregnancy and at 4 days and 1 month postpartum in women with singleton and twin pregnancies.
  
  
  RESULTS
  Urinary levels of cross-linked type I collagen N-telopeptides and C-terminal telopeptides of type I collagen in women with twin pregnancy were significantly higher than those in women with singleton pregnancy and those high levels were observed earlier than those in women with singleton pregnancy. In the cross-sectional study, serum levels of bone-specific alkaline phosphatase, calcium and phosphate in women with twin pregnancy were higher and the levels of 1,25-(OH)2 vitamin D and 25-(OH) vitamin D in women with twin pregnancy were lower than those in women with singleton pregnancy.
  
  
  CONCLUSIONS
  Changes in bone metabolism in women with twin pregnancy are different from those in women with singleton pregnancy. Early and large increases in bone turnover markers allow women with twin pregnancy to meet high fetal demand for calcium during pregnancy.
authors.affiliation: Department of Obstetrics and Gynecology, Institute of Health Biosciences, The University of Tokushima Graduate School, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Nakayama
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yasui
authors.forename: Masanori
authors.initials: M
authors.lastname: Suto
authors.forename: Miki
authors.initials: M
authors.lastname: Sato
authors.forename: Takashi
authors.initials: T
authors.lastname: Kaji
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Uemura
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Maeda
authors.forename: Minoru
authors.initials: M
authors.lastname: Irahara
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D015415:Biomarkers / Q000097:blood; D016723:Bone Remodeling / Q000502:physiology; D001842:Bone and Bones / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D024042:Collagen Type I / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D008137:Longitudinal Studies; D010281:Parathyroid Hormone / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D010710:Phosphates / Q000097:blood; D049590:Postpartum Period / Q000378:metabolism; D011247:Pregnancy / Q000502:physiology*; D059285:Pregnancy, Twin / Q000502:physiology*
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D010710:Phosphates; D000469:Alkaline Phosphatase; D002118:Calcium