The day of initiation of human menopausal gonadotropin stimulation affects follicular growth in in vitro fertilization cycles

The attainment of synchronous follicular development in human menopausal gonadotropin/human chorionic gonadotropin-stimulated cycles for in vitro fertilization (IVF) continues to be a perplexing problem. Two regimens of follicle stimulation for IVF cycles were, therefore, compared. Twenty-nine patients commenced human menopausal gonadotropin (hMG) therapy on day I of the menstrual cycle (Group I), while 30 women received hMG from the third day of the cycle (Group II). The hMG therapy was tailored to the individual patients's response, based on ultrasonographic measurements of follicular size and serum estradiol (E₂) levels. Both groups of patients received a mean of 19.6±1.4 ampules of hMG over a mean of 6.1±0.2 days. The pattern of serum E₂ and progesterone levels in the periovulatory and luteal phase was not affected by the day of initiation of hMG therapy, although Group I patients demonstrated lower (P<0.05) E₂ levels on the 2 days prior to human chorionic gonadotropin (hCG) administration. In terms of follicle growth, Group II follicles consistently demonstrated a significantly (P<0.01, x² test) larger proportion of medium- and large-sized follicles compared to Group I follicles on almost all of the days when ultrasonographic measurements were taken. In addition. Group II follicles demonstrated an earlier shift (day-1) to the larger follicles than Group I follicles (day 0). Significantly (P<0.001) more oocytes were recovered per uspirated follicle in Group II patients, but the fertilization rate per oocyte was greater (P<0.003) for Group I oocytes. Nevertheless, pregnancy rates did not differ between the two groups. It is suggested that a difference between the two groups of patients in the quantity or quality of gonadotropin receptor sites in the early part of the follicular phase may account for both the diminished E₂ production in the follicular phase and the persistent depressed follicular growth in Group I patients.