Nutritional Requirements for Vitamin D in Pregnant Women

This is a three-arm, parallel, double-blind, placebo-controlled dose-response intervention study with vitamin D3. Women will be recruited prior to 18 weeks of gestation and randomised to receive placebo, 10 or 20 mcg/d of vitamin D3 from baseline visit in their first trimester until delivery. Blood samples will be collected at baseline, midpoint and endpoint of the trial, at 10 week intervals, and from the umbilical cord at delivery. A 25-hydroxyvitamin D concentration of 30 nmol/L will be used to denote vitamin D deficiency. Information on maternal anthropometry, diet, lifestyle, sun exposure, blood pressure, iPTH and serum total calcium will also be reported.

Inclusion criteria

• Adult (>18 years)
• No more than 18 weeks gestation
• In good general health
• Low risk pregnancy
• Not consuming >10 mcg/d vitamin D from supplements

Exclusion criteria

• Current smokers
• Diagnosed hypertension
• Known high-risk pregnancy
• Diagnosed medical illness including diabetes mellitus (Types 1 & 2), chronic kidney disease or gastro-intestinal diseases or any illness known to interfere with calcium metabolism (e.g. sarcoidosis).
• Consumption of medications known to interfere with vitamin D metabolism
• Consumption of vitamin D (≥ 10 µg/day) or calcium (≥ 650 mg/d) supplements prior to randomization