Manipulation of the pill-free interval in oral contraceptive pill users: the effect on follicular suppression.
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.
Schlaff
William D
WD
Department of Obstetrics and Gynecology, Section of Reproductive Endocrinology, University of Colorado Health Sciences Center, Denver, 80010, USA. Willaim.Schlaff@uchsc.edu
Lynch
Anne M
AM
Hughes
Heather D
HD
Cedars
Marcelle I
MI
Smith
Deborah L
DL
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*
D003277:Contraceptives, Oral, Combined; D004997:Ethinyl Estradiol; D016912:Levonorgestrel; D017135:Desogestrel