title: Health characteristics and outcomes of two randomized vitamin D supplementation trials during pregnancy: a combined analysis.
abstract: OBJECTIVE
  To assess the safety and health effects of vitamin D supplementation during pregnancy.
  
  
  METHODS
  Datasets from two randomized clinical trials were first analyzed separately then combined for this analysis using a common data dictionary. In the NICHD trial, women were randomized to 400, 2000, or 4000IU vitamin D3/day, stratified by race. In the Thrasher Research Fund trial, participants were randomized to 2000 or 4000IU vitamin D3/day. Study drugs were from the same manufacturing lot for both trials. Identical questionnaires were given for comparable sociodemographics & clinical characteristics. Outcome measures were: [1] maternal and neonatal 25(OH)D achieved, and [2] maternal comorbidities of pregnancy (COP). SAS 9.3 was used for all analyses.
  
  
  RESULTS
  In the combined cohort, there were 110 controls, 201 in the 2000IU group, and 193 in the 4000IU group. No differences between groups in baseline 25(OH)D were found; however, delivery and cord blood values were greater in the 4000IU group (p<0.0001), an effect that persisted even after controlling for race and study. A greater percent were vitamin D replete in the 4000IU group (p<0.0001). There was a trend where the 4000IU group had decreased rates of comorbidities of pregnancy. There was a strong association between COP and final maternal 25(OH)D; an effect that persisted even after controlling for race and study (p=0.006).
  
  
  CONCLUSIONS
  Supplementation with 4000IU/day was associated with lower risk of hypovitaminosis D than Control and 2000IU groups. While not statistically significant, there was a trend toward lower rates of COP as supplementation dose increased. Maternal delivery 25(OH)D was inversely associated with any comorbidity of pregnancy, with fewer events as 25(OH)D increased. Future studies are needed to confirm these findings and determine the mechanisms of action of such effects. This article is part of a Special Issue entitled 'Vitamin D Workshop'.
authors: Division of Neonatology, Department of Pediatrics, Medical University of South Carolina, Charleston, SC 29425, United States. wagnercl@musc.edu
authors: Carol L
authors: CL
authors: Wagner
authors: Rebecca B
authors: RB
authors: McNeil
authors: Donna D
authors: DD
authors: Johnson
authors: Thomas C
authors: TC
authors: Hulsey
authors: Myla
authors: M
authors: Ebeling
authors: Christopher
authors: C
authors: Robinson
authors: Stuart A
authors: SA
authors: Hamilton
authors: Bruce W
authors: BW
authors: Hollis
mesh_terms: D019587:Dietary Supplements; D004311:Double-Blind Method; D004872:Ergocalciferols / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011248:Pregnancy Complications / Q000517:prevention & control*; D011295:Prenatal Care; D016032:Randomized Controlled Trials as Topic / Q000639:trends; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications / Q000517:prevention & control
chemical_list: D004872:Ergocalciferols; D014807:Vitamin D; C104450:25-hydroxyvitamin D