Impact of Maternal Body Weight on Vitamin D Status During Pregnancy

Research shows high levels of vitamin D deficiency in pregnant women in Northern Ireland. Body composition is a determinant of vitamin D status. Vitamin D is a fat soluble vitamin and therefore may be hidden within the adipose/fat tissue in overweight/obese individuals. All pregnant and breastfeeding women are advised to take a daily supplement containing 10μg vitamin D. The investigators hypothesise that overweight/ obese pregnant women have a lower vitamin D status than their leaner counterparts at the start of pregnancy and may need a higher daily supplementation to achieve a sufficient status.

The investigators propose a randomised supplementation study where pregnant women (n 240) from the Western Health and Social Care Trust Area will be invited to take part.

Inclusion criteria: pregnant women first trimester, without current pregnancy related complications, singleton pregnancy, aged ≥18 years, with Body Mass Index (BMI) > 18.5kg /m².

Participants will be randomised to receive either 0μg (placebo) plus a multivitamin or 10μg vitamin D plus a multivitamin from 12 weeks gestation until delivery. The multivitamin already contains 10μg vitamin D; Therefore participants will be randomised to receive a total of 10μg or 20μg vitamin D.

Blood samples (20mls) will be taken at 12, 28 and 36 weeks gestation. A sample of blood will be taken from the cord after delivery. Vitamin D status is the main outcome measurement. All blood samples will be analysed for vitamin D and other associated metabolites. Data will be collected on health and lifestyle, supplementation use and food intake. Body composition measurements will be recorded at each appointment and infant anthropometric measurements will be taken from the maternal notes after delivery. Findings from this research will be used to inform nutrition policy on appropriate vitamin D supplementation levels in pregnancy which may be dependent upon pre pregnancy BMI.