title: Supplemental folic acid in pregnancy and maternal cancer risk.
abstract: BACKGROUND
  There is evidence that increased intake of folate protects against the development of several types of cancer. Some studies have, however, raised concern about the safety of folate in relation to cancer risk. Here we examined the risk of maternal cancer after intake of supplemental folic acid in pregnancy.
  
  
  METHODS
  This is a population-based cohort study comprising 429,004 women with data from the Medical Birth Registry of Norway, the Cancer Registry of Norway, and other national registries from 1999 to 2010. Altogether 3781 cancer cases were identified during follow-up (average 7 years). Cox proportional hazards regression models were used to estimate hazard ratios of maternal cancer according to folic acid use prior to and during one or two or more pregnancies as compared to no supplement use.
  
  
  RESULTS
  Folic acid supplementation use had no overall effect on cancer risk in women using folic acid supplementation in one (HR 1.08; 95% CI 1.00-1.18) or two or more pregnancies (HR 1.06; 95% CI 0.91-1.22) (ptrend=0.12). Analyses of 13 cancer types revealed no associations between folic acid and cancer.
  
  
  CONCLUSIONS
  Folic acid supplementation before and during pregnancy had no overall effect on maternal cancer risk.
  
  
  CONCLUSIONS
  Folic acid substitution before and/or during pregnancy does not increase the short-term overall maternal cancer risk.
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Norway; Department of Obstetrics and Gynecology, Haukeland University Hospital, Bergen, Norway. Electronic address: jan.mortensen@igs.uib.no.
authors.forename: Jan Helge Seglem
authors.initials: JH
authors.lastname: Mortensen
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Norway; Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway.
authors.forename: Nina
authors.initials: N
authors.lastname: Øyen
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Norway.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Fomina
authors.affiliation: Department of Epidemiology Research, National Health Surveillance and Research, Statens Serum Institut, Copenhagen, Denmark; Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark; Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Mads
authors.initials: M
authors.lastname: Melbye
authors.affiliation: Cancer Registry of Norway, Oslo, Norway.
authors.forename: Steinar
authors.initials: S
authors.lastname: Tretli
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Norway; Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: Stein Emil
authors.initials: SE
authors.lastname: Vollset
authors.affiliation: Department of Global Public Health and Primary Care, University of Bergen, Norway; Cancer Registry of Norway, Oslo, Norway.
authors.forename: Tone
authors.initials: T
authors.lastname: Bjørge
mesh_terms: D000328:Adult; D015331:Cohort Studies; D019587:Dietary Supplements / Q000009:adverse effects*; D005260:Female; D005492:Folic Acid / Q000009:adverse effects*; D006801:Humans; D009369:Neoplasms / Q000453:epidemiology*; D009664:Norway / Q000453:epidemiology; D011247:Pregnancy; D016016:Proportional Hazards Models; D012042:Registries; D012306:Risk
chemical_list: D005492:Folic Acid
keywords: Cohort study; Folic acid supplementation; Maternal cancer; Pregnancy