Influence of the duration of the oestradiol rise on the success rate in GnRH analogue/HMG-stimulated IVF cycles

The influence of the duration of the serum oestradiol (E2) rise before human chorionic gonadotrophin (HCG) injection on the outcome of in-vitro fertilization (IVF) cycles was investigated. Two different stimulation protocols were compared. In 218 cycles, the Norfolk protocol for stimulation with human menopausal gonadotrophin (HMG) was used (protocol A). In 235 cycles, pituitary function was suppressed by a single injection of a long-acting GnRH analogue ('Decapeptyl microcapsules') before HMG stimulation was started (protocol B). The overall pregnancy rates were significantly higher with protocol B (22% per puncture, 21% per started cycle) than with protocol A (14% per puncture, 9% per started cycle). For each interval of E2 rise duration (5-11 days), the fertilization rates (per oocyte) and the pregnancy rates (per puncture) were evaluated. There was a clear-cut maximum of the pregnancy rates for 6 and 7 days of E2 rise (21 and 16% respectively) for protocol A. For protocol B, pregnancy rates were generally higher than for protocol A. There was also a maximum of the pregnancy rates for 6 (32%) and 7 (29%) days of E2 rise but this maximum was not as clear-cut as for protocol A. The fertilization rates showed no significant differences for each interval of E2 rise in both groups (between 63 and 89%). Therefore, it is concluded that endometrial maturity, and not the oocyte's ability for fertilization, is the most critical factor for success in IVF cycles.(ABSTRACT TRUNCATED AT 250 WORDS)