The effect of ethinyl estradiol on endometrial thickness and uterine volume during ovulation induction by clomiphene citrate

Objective To assess the deleterious effect of clomiphene citrate (CC) on the development of the endometrium and its improvement by the addition of ethinyl estradiol (E 2 ). Participating Patients Infertility-treated patients, monitored for induction of ovulation or timing of insemination (control group). Design We studied four groups of women during an ovulatory cycle with various treatment schedules. Group 1: untreated patients; group 2: patients treated by CC; group 3: patients treated by CC + ethinyl E 2 ; group 4: patients treated by human menopausal gonadotropin. Follow-up of the patients was done by vaginal ultrasonography and measurements of blood E 2 . Results In the group treated by CC, both endometrial thickness and uterine volume growth during the follicular phase were lower as compared with untreated controls and menotropin-treated patients. The addition of ethinyl E 2 to these patients reversed this deletrious effect of CC without interfering with ovulation. Conclusion Ethinyl E 2 may reverse the deleterious effect of CC on endometrial development during the follicular phase.