Controlled ovarian hyperstimulation:: Does prolonged stimulation justify cancellation of in vitro fertilization cycles?

Background. In daily practice, assisted reproductive technology (ART) cycles are often cancelled under the assumption that a prolonged stimulation period lowers the likelihood of an appropriate ovarian response. The aim of the present study was to determine whether a prolonged cycle has an adverse effect on achievement of pregnancy. Methods. The study sample included consecutive women enrolled in our ART unit between 1999 and 2001 who were treated with the mid-luteal long suppressive gonadotropin-releasing hormone protocol. Data were collected prospectively on a computerized database and evaluated at the end of the study. Prolonged stimulation was defined as a stimulation period of more than two standard deviations (SD) above the mean. Outcome was compared between patients who required prolonged stimulation and those who did not. Results. A total of 1015 consecutive in vitro fertilization (IVF) cycles were performed with the mid-luteal long suppressive protocol during the study period. Thirty-four women required prolonged stimulation. No difference in clinical pregnancy rate was detected between women who received prolonged stimulation and those who did not (9/34, 26.5% vs. 291/981, 29.7%), despite the significantly fewer oocytes retrieved in the prolonged-stimulation group (7.1 +/- 5.2 and 11.6 +/- 6.7 (mean +/- SD), respectively, p < 0.001). Conclusion. The likelihood of achieving pregnancy is not influenced by the length of stimulation. We recommend that IVF cycles should not be discontinued on the grounds of prolonged stimulation alone.