Oral Presentation 33rd ASM of the Australian & New Zealand Bone & Mineral Society 2023

Gestational vitamin D and offspring fracture risk: Do associations persist into mid adolescence? (#34)

Mia Percival 1 , Kara Anderson 1 , Julie Pasco 1 2 3 4 , Sarah Hosking 1 , Lana Williams 1 , Kara Holloway-Kew 1 , Natalie Hyde 1 , John Wark 5 6 7
  1. Deakin University, School of Medicine, IMPACT, The Institute for Mental and Physical Health and Clinical Translation, Geelong, VIC 3220, Australia
  2. Barwon Health, Geelong , VIC, 3220, Australia
  3. Department of Medicine-Western Health, The University of Melbourne, St Albans, VIC, 3021, Australia
  4. Department of Epidemiology and Preventative Medicine, Monash University, Melbourne, VIC, 3181, Australia
  5. Department of Medicine, Royal Melbourne Hospital, University of Melbourne, Parkville, VIC, 3050, Australia
  6. Bone and Mineral Medicine, Royal Melbourne Hospital, Parkville, VIC, 3050, Australia
  7. Department of Diabetes and Endocrinology, Royal Melbourne Hospital, Parkville, VIC, 3050, Australia

Introduction: Previous studies report that maternal vitamin D exposure during pregnancy is associated with offspring bone health in later life. A previous study in the Vitamin D in Pregnancy (VIP) cohort reported on maternal levels of 25-hydroxyvitamin-D (25(OH)D) and offspring fracture risk and found sexual dimorphism of fracture profiles at 10 years of age. We therefore aimed to determine associations between maternal 25(OH)D status and offspring fracture risk at 16 years of age in this cohort.Methods: In total, 475 mother-child pairs were recruited to the VIP study in southeastern Australia. Maternal serum samples were obtained at recruitment (<16 weeks gestation) and/or 28-32 weeks gestation and analysed for 25(OH)D. Radiologically-confirmed incident fractures in children were ascertained from date of birth (2002-2004) until July 16, 2019. Cox proportional hazard models were used to determine associations between maternal 25(OH)D and childhood fracture risk, and final models included maternal age at recruitment, offspring sex, birth weight, gestation length and season of 25(OH)D sample.Results: Complete follow-up data were available for 400 children (mean age 16.1 years at end of follow-up). There were 122 (30.5%) children who had sustained at least one fracture. Higher maternal 25(OH)D (per 10 nmol/L) in early gestation was associated with a decreased fracture risk in boys (HR 0.87; 95% CI 0.77, 0.99); in contrast, the pattern was reversed in girls (HR 1.10; 95% CI 1.00, 1.22). At late gestation, higher maternal 25(OH)D was associated with an increased fracture risk in girls (HR 1.14; 95% CI 1.04, 1.24) but not boys (HR 0.96; 95% CI 0.87, 1.06).Conclusion: The contradictory risk profiles observed at early childhood in this cohort remain in adolescence: while higher maternal 25(OH)D at recruitment was associated with lower fracture risk in boys, higher maternal 25(OH)D at 28-32 weeks gestation was associated with a higher fracture risk in girls.