title: Recent oral contraceptive use and adverse birth outcomes.
abstract: OBJECTIVE
  To examine the possible association between oral contraceptive use and adverse birth outcomes.
  
  
  METHODS
  We conducted a population-based cohort study of pregnant women who used oral contraceptives within 3 months before their last menstrual period. Subjects were divided into three groups, according to the interval (0-30, 31-60, and 61-90 days) between the dispensing date and their last menstrual period. For each exposed subject, 4 subjects without exposure to oral contraceptives were individually matched by infant's year of birth and plurality and by mother's age and parity.
  
  
  RESULTS
  Oral contraceptive use within 30 days prior to the last menstrual period was associated with increased risks of very low birth weight (OR: 3.24, 95% CI: 1.18, 8.92), low birth weight (OR: 1.93, 95% CI: 1.17, 3.20), and preterm birth (OR: 1.61, 95% CI: 1.01, 2.55); however, oral contraceptive use 31-90 days prior to the last menstrual period did not increase the risk of low birth weight or preterm birth.
  
  
  CONCLUSIONS
  Our results indicate the use of oral contraceptives near the time of conception may be associated with an increased risk of low birth weight and preterm birth.
authors.affiliation: McLaughlin Center for Population Health Risk Assessment, Institute of Population Health, University of Ottawa, Ontario, Canada. xikuan.chen@gmail.com
authors.forename: Xi-Kuan
authors.initials: XK
authors.lastname: Chen
authors.forename: Shi Wu
authors.initials: SW
authors.lastname: Wen
authors.forename: Lu-Ming
authors.initials: LM
authors.lastname: Sun
authors.forename: Qiuying
authors.initials: Q
authors.lastname: Yang
authors.forename: Mark C
authors.initials: MC
authors.lastname: Walker
authors.forename: Daniel
authors.initials: D
authors.lastname: Krewski
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003276:Contraceptives, Oral / Q000009:adverse effects*; D005260:Female; D005306:Fertilization / Q000502:physiology*; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D011247:Pregnancy; D011256:Pregnancy Outcome; D047928:Premature Birth / Q000453:epidemiology; D012307:Risk Factors; D012525:Saskatchewan / Q000453:epidemiology; D013997:Time Factors
chemical_list: D003276:Contraceptives, Oral