title: Manipulation of the pill-free interval in oral contraceptive pill users: the effect on follicular suppression.
abstract: OBJECTIVE
  The purpose of this study was to compare follicular suppression that was produced by 3 different oral contraceptive regimens that differ by treatment in the pill-free interval.
  
  
  METHODS
  In a university setting, 54 women were assigned randomly to receive either 20 microg ethinyl estradiol+100 microg levonorgestrel followed by 7 pill-free days, 20 microg ethinyl estradiol+150 microg desogestrel followed by 2 days of placebo then 10 microg ethinyl estradiol for 5 days, or 28 days of 20 microg ethinyl estradiol plus 150 microg desogestrel. Follicular suppression was evaluated by serial ultrasound scans and by serum and urinary hormone levels during a 2-month study period. Data were analyzed by nonparametric statistical tests.
  
  
  RESULTS
  There was a significant difference in follicle count among the 3 groups (P=.005). Women who were treated with a 7-day pill-free interval experienced the least suppression. Estrogen levels were more variable and led to an observation that overweight (body mass index, >25 kg/m(2)) was associated with reduced follicle suppression (relative risk, 1.6; 95% CI, 1.0, 2.7) and higher estrogen levels (relative risk, 5.3; 95% CI, 1.3, 21).
  
  
  CONCLUSIONS
  Contraceptive pill users who were treated with a 7-day pill-free interval demonstrated less follicular suppression than women who were supplemented with either estrogen alone or estrogen plus progestin. Overweight women were less suppressed than women of normal weight.
authors.affiliation: Department of Obstetrics and Gynecology, Section of Reproductive Endocrinology, University of Colorado Health Sciences Center, Denver, 80010, USA. Willaim.Schlaff@uchsc.edu
authors.forename: William D
authors.initials: WD
authors.lastname: Schlaff
authors.forename: Anne M
authors.initials: AM
authors.lastname: Lynch
authors.forename: Heather D
authors.initials: HD
authors.lastname: Hughes
authors.forename: Marcelle I
authors.initials: MI
authors.lastname: Cedars
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Smith
mesh_terms: D000328:Adult; D015992:Body Mass Index; D003277:Contraceptives, Oral, Combined / Q000008:administration & dosage*; D017135:Desogestrel / Q000008:administration & dosage; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D004997:Ethinyl Estradiol / Q000008:administration & dosage; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000008:administration & dosage; D008597:Menstrual Cycle / Q000187:drug effects; D006080:Ovarian Follicle / Q000187:drug effects*
chemical_list: D003277:Contraceptives, Oral, Combined; D004997:Ethinyl Estradiol; D016912:Levonorgestrel; D017135:Desogestrel