SHORTER PILL-FREE INTERVAL IN COMBINED ORAL-CONTRACEPTIVES DECREASES FOLLICULAR DEVELOPMENT

The objective of the study was to determine the suppressive effect on ovarian activity of 20 mu g ethinylestradiol plus 75 mu g gestodene ad ministered for 21 or 23 days. The study was designed as a double-blind , randomized, multicenter trial in 60 women. A pre-treatment cycle, th ree treatment cycles and a post-treatment period were monitored by ova rian ultrasound and by LH, FSH, 17 beta-estradiol and progesterone mea surements every other day. No ovulation and no luteinized, unruptured follicle were observed. Suppression of ovarian activity was more prono unced by the 23-day regimen. 17 beta-Estradiol serum levels during the last six days of a cycle and during the first six days of the next cy cle were significantly less (p < 0.05) in the 23-day regimen. The supe riority of the 23-day regimen in comparison to the el-day regimen with regard to the suppression of ovarian activity was shown in this study . The observed differences in the 17 beta-estradiol levels and follicu lar development between a 21-day and 23-day preparation combine to sug gest that shortening the pill-free interval in combined oral contracep tives may increase the contraceptive safety margin in women on low-dos e formulations.