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Date of Award

Fall 2011

Degree Type

Thesis

Degree Name

Master of Science (MSc)

Department

Medical Sciences

Supervisor

Stephanie Atkinson

Language

English

Abstract

Emerging evidence indicates that in utero exposure to vitamin D metabolites may influence fetal and neonatal bone development. Bone accretion in prenatal and early postnatal life may impact peak bone mass achieved in early adolescence; and peak bone mass is a well-established predictor of osteoporosis risk in later life. Hypothesis: We hypothesized that offspring of mothers with higher serum vitamin D status during pregnancy will have higher whole body BMC z-score and bone size at 3 years of age, after adjustment for confounders. Methods: In a prospective, longitudinal study, 372 mothers with singleton birth were recruited during pregnancy, and maternal blood samples were obtained during the third trimester. Child bone outcome measures at 3 years of age included: whole body BMC, femoral and humeral lengths by DXA. We controlled for other relevant factors such as maternal nutrition, pre-pregnancy BMI, physical activity during pregnancy, maternal BMD, as well as the child’s nutrition at 6 months and 3 years, and the child’s physical activity. Results & Discussion: Maternal vitamin D status during pregnancy did not predict whole body BMC z-score of the child at 3 years of age. Over 92% of Canadian women in our sample were vitamin D sufficient with mean intakes of 435 IU/day from food and supplements and mean serum 25OHD of 111.2 nM. Further, data indicate a potential negative effect on offspring bone size at maternal serum 25OHD concentrations that exceed the upper limit suggested by the most recent DRI report (>125 nM), at which adverse health effects may occur. Our findings may differ from previous studies in the United Kingdom, India and Finland that found a positive relationship between maternal vitamin D status and child bone outcomes due to the high frequency of our mothers that had optimal vitamin D status. In addition, we adjusted for most of the key covariates that were not adjusted for in previous studies, which may contribute to the different findings compared to previous investigations.

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