title: Determinants of microstructural, dimensional and bone mineral changes postpartum in Swedish women.
abstract: During lactation, areal (a) and volumetric (v) bone mineral density (BMD) are known to temporarily decrease. Factors that affect skeletal changes postpartum are not fully elucidated. The aim was to study determinants of the previously observed changes in aBMD at lumbar spine, and cortical vBMD, microstructure and dimensions at ultra-distal tibia postpartum. Women (25-40 years) were studied longitudinally at 2 weeks (baseline) and 4 months (n 81), 12 months (n 79) and 18 months (n 58) postpartum. At each visit, blood samples were collected, body weight and height were measured and information about lactation habits, oestrogen contraceptives and physical activity was obtained. Ca intake was measured using 4-d food diaries at 4 months postpartum. Serum 25-hydroxyvitamin D (25OHD) was analysed by liquid chromatography-tandem MS. Skeletal changes were assessed with dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography. Mean baseline BMI was 24·8 (sd 3·1) kg/m2. Median (quartiles 1-3) duration of total lactation was 8·1 (6·8-10·4) months. Longer duration of full lactation was associated with larger decreases of lumbar spine aBMD and tibia vBMD and microstructure. Higher baseline body weight was associated with smaller decreases in tibia vBMD and microstructure. Higher Ca intake was associated with smaller decreases in tibia cortical vBMD and thickness. Higher baseline 25OHD was only associated with larger decreases in lumbar spine aBMD. In conclusion, lactation and body weight were the main determinants of skeletal changes during the first 18 months postpartum. Ca intake and serum concentrations of 25OHD appear to have different associations with cortical and trabecular bone.
authors.affiliation: Department of Internal Medicine and Clinical Nutrition,Institute of Medicine,Sahlgrenska Academy,University of Gothenburg,Box 459, 405 30 Gothenburg,Sweden.
authors.forename: Petra
authors.initials: P
authors.lastname: Brembeck
authors.affiliation: Department of Internal Medicine and Clinical Nutrition,Institute of Medicine,Sahlgrenska Academy,University of Gothenburg,Box 459, 405 30 Gothenburg,Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Winkvist
authors.affiliation: Department of Internal Medicine and Clinical Nutrition,Institute of Medicine,Sahlgrenska Academy,University of Gothenburg,Box 459, 405 30 Gothenburg,Sweden.
authors.forename: Claes
authors.initials: C
authors.lastname: Ohlsson
authors.affiliation: Department of Internal Medicine and Clinical Nutrition,Institute of Medicine,Sahlgrenska Academy,University of Gothenburg,Box 459, 405 30 Gothenburg,Sweden.
authors.forename: Mattias
authors.initials: M
authors.lastname: Lorentzon
authors.affiliation: Department of Internal Medicine and Clinical Nutrition,Institute of Medicine,Sahlgrenska Academy,University of Gothenburg,Box 459, 405 30 Gothenburg,Sweden.
authors.forename: Hanna
authors.initials: H
authors.lastname: Augustin
keywords:  25OHD 25-hydroxyvitamin D;  BUGA Benmetabolism Under Graviditet och Amning (Bone Metabolism During Pregnancy and Lactation);  PAL physical activity level;  aBMD areal bone mineral density;  vBMD volumetric bone mineral density; 25-Hydroxyvitamin D; Bone mineral density; Dual-energy X-ray absorptiometry; High-resolution peripheral quantitative computed tomography; Lactation; Postpartum; Vitamin D