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Follicular development in a 7-day versus 4-day hormone-free interval with an oral contraceptive containing 20 mcg ethinyl estradiol and 1 mg norethindrone acetate.

Author(s): Rible RD, Taylor D, Wilson ML, Stanczyk FZ, Mishell DR Jr

Affiliation(s): Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA. r.rible@gmail.com

Publication date & source: 2009-03, Contraception., 79(3):182-8. Epub 2008 Nov 17.

Publication type: Research Support, Non-U.S. Gov't

BACKGROUND: Combined oral contraceptive (COC) formulations with 20 mcg ethinyl estradiol (EE) have a greater incidence of ovarian hormone production and follicular development, which can be managed by shortening the number of hormone-free days per COC cycle. This study evaluates differences in follicular development during a 7-day versus 4-day hormone-free interval in a COC regimen with 20 mcg EE and 1 mg norethindrone acetate. STUDY DESIGN: Forty-one healthy women were randomized in an open-label fashion to this formulation in either a 24/4 or a 21/7 day regimen for three cycles. Estradiol, progesterone, follicle-stimulating hormone, luteinizing hormone and inhibin B were measured daily from Cycle 2, Day 21 to Cycle 3, Day 3 and on Day 7 of Cycle 3. Follicular diameter and Hoogland score were calculated on Cycle 2, Days 21, 24 and 28 and Cycle 3, Days 3 and 7. RESULTS: Sixty-six percent of subjects in the 21/7 group and 70% of the subjects in the 24/4 group developed a follicle greater than 10 mm diameter. Ovarian steroid hormone levels, Hoogland scores and bleeding patterns were not statistically significant between the groups. CONCLUSION: In contrast to prior studies, this analysis suggests no difference in follicle development or bleeding patterns among women receiving a 21/7 or 24/4 regimen of a 20-mcg EE/1-mg norethindrone acetate COC.

Page last updated: 2009-02-08

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