title: Continuous combination oral contraceptive pills to eliminate withdrawal bleeding: a randomized trial.
abstract: OBJECTIVE
  To compare bleeding profiles of a traditional 28-day oral contraceptive pill cycle with continuous administration.
  
  
  METHODS
  After a 28-day run-in cycle, women were randomized to either 28-day cycles (21 active pills and a pill-free week) or continuous use of the same 20 microg ethinyl estradiol/100 microg levonorgestrel formulation for 12 study cycles (336 days). The number of bleeding and spotting days were measured by daily diary. A subset underwent cycle 1 (n = 16), and nine (n = 14) pelvic ultrasound and endometrial histology sampling. Blood pressure, weight, hemoglobin, and adverse events were measured at revisit. The sample size with 80% power to detect a 67% reduction in bleeding days required 27 subjects in each arm.
  
  
  RESULTS
  Of the 79 subjects randomized, 28 (70%) of the 28-day cycle and 32 (82%) of the continuous-use subjects completed the entire study (P =.6). With continuous use, 49%, 68%, and 88% of women reported no bleeding during cycles 2, 6, and 12, respectively. Amenorrhea or infrequent bleeding was present in 68% of continuous users during cycles 1-3 and increased to 88% during cycles 10-12. Spotting during cycle days 1-21 increased initially with continuous use but reduced over time, and by 9 months was less than the spotting reported by cyclic users. Adverse events, blood pressure, weight, and hemoglobin findings were similar between groups.
  
  
  CONCLUSIONS
  Extension of the 28-day oral contraceptive cycle to continuous use with a low-estrogen dose combination oral birth control pill resulted in significantly fewer bleeding days.
authors.affiliation: Departments of Obstetrics & Gynecology, University of Washington, Seattle, Washington, USA. lmiller@u.washington.edu
authors.forename: Leslie
authors.initials: L
authors.lastname: Miller
authors.forename: James P
authors.initials: JP
authors.lastname: Hughes
mesh_terms: D000328:Adult; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D004717:Endometrium / Q000000981:diagnostic imaging / Q000473:pathology; D004997:Ethinyl Estradiol / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000008:administration & dosage*; D008597:Menstrual Cycle / Q000187:drug effects*; D016896:Treatment Outcome; D014463:Ultrasonography; D014592:Uterine Hemorrhage / Q000517:prevention & control*
chemical_list: D003277:Contraceptives, Oral, Combined; D004997:Ethinyl Estradiol; D016912:Levonorgestrel