Maternal obesity and vitamin D supplementation: implications for maternal and fetal bone health.

Diet Nutrition

Pregnant women who are overweight or obese are particularly vulnerable to vitamin D insufficiency owing to the higher physiological requirement and lower status (25-hydroxyvitamin D, 25(OH)D concentrations) associated with obesity. Vitamin D is involved in calcium and phosphate homeostasis and is essential for the maintenance of bone health. Maternal vitamin D supply is the main source of fetal vitamin D and vitamin D status of the neonate has been shown to be highly correlated with maternal vitamin D status, accounting for 60-80% of infants’ status at delivery. Vitamin D deficiency during pregnancy is associated with poor fetal and postnatal growth and it has been observed that neonates of obese mothers had significantly lower vitamin D status in cord blood compared to neonates of normal weight mothers despite no difference in maternal 25(OH)D status. During pregnancy, the maternal physiology adapts to meet the increased calcium demands of the fetus. The effect of this adaptation on maternal and fetal bone status, particularly in the context of obesity, combined with a low vitamin D status is not fully understood. While numerous studies have examined vitamin D supplementation in pregnancy, none have examined the impact of obesity on bone turnover markers in response to vitamin D supplementation throughout pregnancy.

We have recently completed a large intervention study in pregnant women to assess the effect of supplementation (10μg-vs-20μg vitamin D_3/d) throughout pregnancy (from 12 weeks gestation until delivery) on vitamin D status of normal weight, overweight and obese pregnant women and on infant cord blood, using a double-blind randomised vitamin D intervention study (MO-VITD). Based on our findings of the high prevalence of vitamin D insufficiency in early pregnancy, maternal vitamin D supplementation of 20µg/d may be advisable to maintain maternal vitamin D status in pregnant women in Northern Ireland.

This PhD will be a continuation of our work and will aim to investigate the impact of obesity and vitamin D supplementation on the associated maternal and fetal bone turnover markers.

This aim will be addressed through the completion of the following analysis:

·        The association between maternal adiposity, vitamin D status and bone turnover markers: a systematic review

·        To investigate the impact of maternal adiposity on bone turnover marker status in early pregnancy.

·        To investigate the effect of supplementation of 10μg vs 20μg vitamin D3/d on maternal and fetal bone turnover markers in normal weight, overweight and obese pregnant women

·        To assess the impact of supplementation of 10μg vs 20μg vitamin D3/d during pregnancy on bone density in the offspring (MOVITD follow-up study).

For details and how to apply please see: https://www.ulster.ac.uk/doctoralcollege/find-a-phd/794568

For further information please contact: Dr Mary McCann: [Email Address Removed]

Interviews by Faculties: April 2021

Outcome letters sent to applicants: Late April/early May 2021

Scholarships commence: September 2021

 Eligibility Criteria

·        Applicants should hold, or expect to obtain, a first or upper second-class honours degree in a subject relevant to the proposed area of study. Applicants deemed by Senate to hold an equivalent qualification will also be considered.

·        Applicants who already hold a doctoral degree or who have been registered on a programme of research leading to the award of a doctoral degree on a full-time basis for more than one year, or part-time equivalent, funded from any source, including self-financing researchers, are NOT eligible for a scholarship.

·        All applicants should also hold a relevant English language qualification.  All applications for scholarships will be considered on a competitive basis and with regard to the applicant’s qualifications, skills, experience and interests.

·        Competition for funded entry is very high. It is important that all parts of the application process are completed in accordance with the instructions.  All applicants are advised to discuss their application with the staff noted within the project description prior to submission.

·        Applicants should note that disclosure of disability or personal circumstances should be made as part of the application process or as soon as possible thereafter in order to facilitate any necessary accommodation.