title: Bone turnover and mineral metabolism in the last trimester of pregnancy: effect of multiple gestation.
abstract: OBJECTIVE
  To test the hypothesis that maternal bone turnover and mineral stress are greater in multiple pregnancy than in singleton pregnancy.
  
  
  METHODS
  We measured serum markers of bone turnover and mineral stress in 17 multiple and 30 singleton pregnancies during the third trimester.
  
  
  RESULTS
  Serum 25(OH) vitamin D, a marker of vitamin D intake, was higher (61 +/- 5 versus 39 +/- 2 ng/mL, P < .001), and 1,25(OH)2 vitamin D was lower (50 [95% confidence interval (CI) 24-102] versus 64 pg/mL [95% CI 30-135], P = .03) in multiple than in singleton pregnancy. Carboxyterminal telopeptide of type I collagen, a marker of bone resorption, increased with gestational duration and was higher in multiple gestation (5.8 [95% CI 3.3-10.1] versus 4.4 ng/mL [95% CI 2.5-7.8], P = .005). Carboxyl-terminal propeptide of type 1 procollagen, a marker of bone formation, increased with gestational duration and was not different between groups (110 [95% CI 36-337] versus 99 ng/mL [95% CI 34-286], P = .5). Calcitonin increased with gestational duration and was not different between groups (7.0 [95% CI 3.7-13.0] versus 7.8 pg/mL [95% CI 4.0-15.4], P = .37). Parathyroid hormone was not different between groups and decreased with increasing maternal age.
  
  
  CONCLUSIONS
  Bone turnover indices increased with gestational duration. The bone resorption index was greater in multiple than in singleton gestation. Serum 25(OH) vitamin D was greater and 1,25(OH)2 vitamin D was lower in multiple gestation, presumably because of greater consumption of vitamin D and minerals by women carrying more than one fetus.
authors.affiliation: Children's Hospital Research Foundation, Perinatal Research Institute, University of Cincinnati Medical Center, Ohio, USA.
authors.forename: F A
authors.initials: FA
authors.lastname: Okah
authors.forename: R C
authors.initials: RC
authors.lastname: Tsang
authors.forename: R
authors.initials: R
authors.lastname: Sierra
authors.forename: K K
authors.initials: KK
authors.lastname: Brady
authors.forename: B L
authors.initials: BL
authors.lastname: Specker
mesh_terms: D000328:Adult; D001842:Bone and Bones / Q000378:metabolism*; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D008903:Minerals / Q000378:metabolism*; D011247:Pregnancy / Q000378:metabolism*; D011263:Pregnancy Trimester, Third; D011272:Pregnancy, Multiple / Q000378:metabolism*
chemical_list: D008903:Minerals