Correlation of ultrasonic measurement of ovarian follicle size and serum estradiol levels in ovulatory patients following clomiphene citrate for in vitro fertilization.

Ovarian follicle development was investigated in 38 normally cycling women who received clomiphene citrate, 150 mg per day for 5 days, to maximize follicular development. Ultrasonic determination of follicle growth was performed on a daily basis with a real-time sector scanner and correlated with daily concentrations of estradiol (E2) in the peripheral serum as measured by rapid radioimmunoassay. Human Chorionic gonadotropin was given to induce ovulation, and the day of injection was considered day 0. Mean concentrations of E2 reached a maximum of 1,150 +/- 65 pg/ml on day 0. Mean diameter of the dominant follicle increased to 22.1 +/- 0.4 on day 0. When peripheral concentrations of E2 were correlated with diameter and total follicular volume it was found that plasma E2 levels varied, depending on the number of follicles seen on ultrasound examination, with a mean E2 value of 459 +/- 18.9 pg/ml per follicle per day. Multiple growth of follicles occur with artificial induction of ovulation; therefore, the use of ultrasound is an important parameter to assess follicular maturation and the timing of ovulation more precisely.