title: Moderate alcohol intake and menstrual cycle characteristics.
abstract: OBJECTIVE
  Does moderate alcohol intake affect menstrual cycle characteristics among women in the Danish population?
  
  
  CONCLUSIONS
  Levels of alcohol exposure as seen in this study do not substantially affect the menstrual cycle.
  
  
  BACKGROUND
  Animal studies indicate alcohol-induced disruptions of the reproductive system, but previous epidemiological studies addressing the possible association between alcohol intake and the menstrual cycle are sparse.
  
  
  METHODS
  A cross-sectional study with retrospectively collected data including 82 146 pregnant Danish women in the Danish National Birth Cohort (DNBC) enrolled during the years 1996-2002.
  
  
  METHODS
  Information on weekly alcohol consumption and menstrual cycle characteristics before pregnancy was obtained through a computer-assisted telephone interview in pregnancy Week 12-16. The associations between weekly alcohol consumption and menstrual cycle irregularity (≥7 days difference between cycles) and length (short cycle: ≤24 days, long cycle: ≥32 days) were analysed using logistic regression with weekly alcohol intake categorized into abstainers (0 drinks per week), low (0.5-2.0 drinks per week), moderate (2.5-14.0 drinks per week) and high (14.0-86.5 drinks per week). Estimates are given as adjusted odds ratios with 95% confidence intervals.
  
  
  RESULTS
  The overall participation rate was 60% of the women invited. We found that a high weekly alcohol consumption was not associated with menstrual cycle disturbances. We observed higher odds of irregular and short cycles among abstainers when compared with women with a low weekly alcohol consumption, but found no trend of more cycle disturbances with higher alcohol consumption.
  
  
  CONCLUSIONS
  Possible limitations in our study include a risk of selection bias due to the moderate participation rate and the use of retrospective information on alcohol exposure and menstrual cycle characteristics before getting pregnant. The higher odds of irregular and short cycles among abstainers may reflect other health problems in these women rather than an actual effect of alcohol on the menstrual cycle.
  
  
  CONCLUSIONS
  The generalizability of the study results is restricted to women who manage to conceive and women who do not use oral contraceptives within 2 months before getting pregnant. This study suggests that the menstrual cycle is not substantially affected by higher alcohol consumption among the participating women.
  
  
  BACKGROUND
  Supported by a scholarship from Aarhus University Research Foundation. The Danish National Research Foundation has established the Danish Epidemiology Science Centre that initiated and created the DNBC. The cohort is furthermore a result of a major grant from this Foundation. Additional support for the DNBC is obtained from the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation and the Health Foundation. No conflict of interest declared.
authors.affiliation: Department of Occupational Medicine, Danish Ramazzini Centre, Aarhus University Hospital, Noerrebrogade 44, Build. 2C, Aarhus DK-8000, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Lyngsø
authors.forename: G
authors.initials: G
authors.lastname: Toft
authors.forename: B B
authors.initials: BB
authors.lastname: Høyer
authors.forename: K
authors.initials: K
authors.lastname: Guldbrandsen
authors.forename: J
authors.initials: J
authors.lastname: Olsen
authors.forename: C H
authors.initials: CH
authors.lastname: Ramlau-Hansen
mesh_terms: D000328:Adult; D000428:Alcohol Drinking; D000434:Alcoholic Beverages; D015331:Cohort Studies; D003276:Contraceptives, Oral / Q000008:administration & dosage; D003430:Cross-Sectional Studies; D003718:Denmark; D005260:Female; D006801:Humans; D008597:Menstrual Cycle / Q000187:drug effects*; D016017:Odds Ratio; D011247:Pregnancy; D012189:Retrospective Studies
chemical_list: D003276:Contraceptives, Oral
keywords: alcohol drinking; female reproduction; menstrual cycle