title: Association Between Use of Oral Contraceptives and Folate Status: A Systematic Review and Meta-Analysis.
abstract: OBJECTIVE
  To conduct a systematic review and meta-analysis of the effect of oral contraceptive use on plasma and red blood cell (RBC) folate concentrations.
  
  
  METHODS
  We searched Medline, EMBASE, Web of Science, and the Cochrane library for human studies published from inception to June 2013 evaluating oral contraceptive use and folate status. Case-control studies, cohort studies, and clinical trials were included. A random-effects model of outcomes was used for the meta-analysis.
  
  
  RESULTS
  A total of 2831 women in 17 studies were included in the analysis. In those whose plasma folate concentrations were available, there was a significant folate-lowering effect of oral contraceptives observed (mean reduction 1.27 µg/L; 95% CI 1.85 to 0.69, P < 0.001). Similarly, after analyzing data from 1389 women in 12 studies whose RBC folate concentrations were available, significantly lower folate status was observed among oral contraceptive users (mean reduction 59.32 µg/L; 95% CI 58.03 to 23.04, P < 0.001).
  
  
  CONCLUSIONS
  Because of the reduction in blood folate concentrations associated with the use of oral contraceptives, it is critical for women of childbearing age to continue folate supplementation during oral contraceptive use.
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto ON; The Motherisk Program, Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children, Toronto ON.
authors.forename: Mahvash
authors.initials: M
authors.lastname: Shere
authors.affiliation: The Motherisk Program, Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children, Toronto ON; Department of Pharmacology and Toxicology, University of Toronto, Toronto ON.
authors.forename: Priya
authors.initials: P
authors.lastname: Bapat
authors.affiliation: The Motherisk Program, Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children, Toronto ON.
authors.forename: Cheri
authors.initials: C
authors.lastname: Nickel
authors.affiliation: Department of Pharmacology and Toxicology, University of Toronto, Toronto ON; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto ON.
authors.forename: Bhushan
authors.initials: B
authors.lastname: Kapur
authors.affiliation: Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto ON; The Motherisk Program, Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children, Toronto ON; Department of Pharmacology and Toxicology, University of Toronto, Toronto ON.
authors.forename: Gideon
authors.initials: G
authors.lastname: Koren
mesh_terms: D003276:Contraceptives, Oral / Q000627:therapeutic use*; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D005492:Folic Acid / Q000097:blood*; D006801:Humans; D010949:Plasma / Q000378:metabolism; D012959:Socioeconomic Factors
chemical_list: D003276:Contraceptives, Oral; D005492:Folic Acid
keywords: RBC folate; contraception; family planning; folic acid supplementation; oral contraceptives; plasma folate; pregnancy