title: Folic acid supplement use and menstrual cycle characteristics: a cross-sectional study of Danish pregnancy planners.
abstract: OBJECTIVE
  To examine the association between folic acid (FA) supplementation obtained through either single FA tablets or multivitamins (MVs) and menstrual cycle characteristics among 5386 women aged 18-40 years, enrolled in an Internet-based study of Danish women attempting pregnancy during 2007-2011.
  
  
  METHODS
  In a cross-sectional study, we used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations of FA supplementation with menstrual cycle regularity; short (<27 days), long (30-33 days), and very long (≥34 days) cycle lengths; and duration and intensity of menstrual bleeding.
  
  
  RESULTS
  Compared with nonuse, FA supplementation was associated with reduced odds of short cycle length (OR = 0.80, 95% CI: 0.68-0.94) and a trend toward increased odds of very long cycle length (OR = 1.21, 95% CI: 0.87-1.68) compared with cycle length of 27-29 days. The inverse association with short cycle length was stronger among 18- to 30-year-old women (OR = 0.68, 95% CI: 0.53-0.87), nulliparous women (OR = 0.66, 95% CI: 0.52-0.84), and women who used both FA and MVs (OR = 0.75, 95% CI: 0.60-0.95). We found no clear association between FA supplementation and cycle regularity and duration and intensity of menstrual bleeding.
  
  
  CONCLUSIONS
  FA supplementation was inversely associated with short menstrual cycle length. This association was strongest among women aged 18-30 years, nulliparous women, and women who used both FA and MVs.
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark. Electronic address: hc@clin.au.dk.
authors.forename: Heidi T
authors.initials: HT
authors.lastname: Cueto
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Anders H
authors.initials: AH
authors.lastname: Riis
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA.
authors.forename: Elizabeth E
authors.initials: EE
authors.lastname: Hatch
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA; Slone Epidemiology Center, Boston University, Boston, MA.
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Wise
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; Department of Epidemiology, Boston University School of Public Health, Boston, MA; RTI Health Solutions, Research Triangle Park, Durham, NC.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rothman
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; Department of Epidemiology, Boston University School of Public Health, Boston, MA.
authors.forename: Henrik T
authors.initials: HT
authors.lastname: Sørensen
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Mikkelsen
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D003267:Contraception; D003430:Cross-Sectional Studies; D003718:Denmark; D019587:Dietary Supplements; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000494:pharmacology*; D015438:Health Behavior; D006801:Humans; D016015:Logistic Models; D008597:Menstrual Cycle / Q000187:drug effects*; D008598:Menstruation / Q000187:drug effects; D016017:Odds Ratio; D010298:Parity; D013997:Time Factors; D055815:Young Adult
chemical_list: D005492:Folic Acid
keywords: Folic acid; Menstrual cycle characteristics; Preconceptional supplements; Vitamin supplementation