The effect of maternal vitamin D concentration on fetal bone

Ioannou, C., Javaid, M.K., Mahon, P.A., Yaqub, M.K., Harvey, N.C., Godfrey, K.M., Noble, J.A., Cooper, C. and Papageorghiou, A.T. (2012) The effect of maternal vitamin D concentration on fetal bone. Journal of Clinical Endocrinology & Metabolism, 97 (11), E2070-E2077. (doi:10.1210/jc.2012-2538). (PMID:22990090)

Abstract

CONTEXT: Vitamin D deficiency during pregnancy may be associated with suboptimal fetal growth, but direct evidence is lacking. Objectives: The aim of the study was to validate a method for fetal femur volume (FV) measurement using three-dimensional ultrasound and to detect correlations between FV and maternal vitamin D concentration.

DESIGN, SETTING, AND PARTICIPANTS: A novel method for assessing FV consists of three ultrasound measurements-femur length, proximal metaphyseal diameter (PMD), and midshaft diameter-and a volume equation; this was validated by comparing ultrasound to computed tomography measurements in six pregnancies after mid-trimester termination. This method was then applied in a cohort of healthy pregnant women participating in the Southampton Women Survey. Fetal three-dimensional ultrasound and maternal 25-hydroxyvitamin D [25(OH)D] levels were performed at 34 wk; dual-energy x-ray absorptiometry of the newborn was performed shortly after birth. Univariate and multiple linear regression analyses were performed between maternal characteristics and fetal outcomes. Main Outcome Measures: We performed ultrasound measurements of the fetal femur.

RESULTS: In 357 pregnant participants, serum 25(OH)D correlated significantly with FV (P = 0.006; r = 0.147) and PMD (P = 0.001; r = 0.176); FV also demonstrated positive univariate correlations with maternal height (P < 0.001; r = 0.246), weight (P = 0.003; r = 0.160), triceps skinfold thickness (P = 0.013; r = 0.134), and a borderline negative effect from smoking (P = 0.061). On multiple regression, independent predictors of FV were the maternal height and triceps skinfold thickness; the effect of 25(OH)D on FV was attenuated, but it remained significant for PMD.

CONCLUSION: Using a novel method for assessing FV, independent predictors of femoral size were maternal height, adiposity, and serum vitamin D. Future trials should establish whether pregnancy supplementation with vitamin D is beneficial for the fetal skeleton, using FV and PMD as fetal outcome measures.

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Contributors

Author: N.C. Harvey

Author: K.M. Godfrey

Author: C. Cooper

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