McLean 2012.

Trial name or title	Does vitamin D supplementation in pregnancy improve maternal glucose metabolism or prevent gestational diabetes?
Methods	Randomised controlled trial where pregnant women will be allocated to take high‐dose vitamin D supplementation (5000 IU/day) or standard dose pregnancy vitamin supplementation (400 IU vitamin D daily), administered as an oral capsule, from the time of the first antennal clinic visit (around 12 weeks' gestation) until delivery. Patients will be recruited at their first antenatal clinic visit. Baseline tests will exclude pre‐existing diabetes, hypercalcaemia or vitamin D toxicity. Treatment will be stratified according to baseline serum vitamin D levels and randomised by the trial pharmacist using opaque envelopes containing a treatment allocation. Patient, treating clinician and researchers will remain blinded to treatment group. The trial will be conducted in Australia.
Participants	Inclusion criteria: pregnancy, less than 20 weeks' gestation at recruitment, 18 years and above Exclusion criteria: known diabetes, calcium metabolic disorder, multiple pregnancy
Interventions	Pregnant women will be randomly allocated to take high‐dose vitamin D supplementation (5000IU/day) or standard dose pregnancy vitamin supplementation (400 IU vitamin D daily), administered as an oral capsule, from the time of the first antenatal clinic visit (around 12 weeks gestation) until delivery. Women in the control group will receive a standard dose of vitamin D supplementation (as in commonly used in pregnancy multivitamin preparations).
Outcomes	Maternal Primary: Incidence of gestational diabetes (assessed by a 75g OGTT at 26‐28 weeks of gestation) Infant Primary: Birthweight (g) Birth length (cm) Head circumference at birth (cm)
Starting date	June 2017
Contact information	Samantha Hoffman, MD Tel. No: 612‐626‐3111 Email: kehoe018@umn.edu University of Minnesota Medical Center Minneapolis, Minnesota, United States, 55455
Notes	Funding: sponsored by University of Minnesota – Clinical and Translational Science Institute Declarations of interest among primary researchers: NA