Predictive value of the number of oocytes retrieved at ultrasound-directed follicular aspiration with regard to fertilization rates and pregnancy outcome in intracytoplasmic sperm injection treatment cycles

Objective: To determine the number of oocytes sufficient for satisfactory fertilization and pregnancy rates in intracytoplasmic sperm injection cycles. Design: A retrospective analysis. Setting: A private assisted conception unit. Patient(s): Women in whom at least one oocyte was retrieved in consecutive ultrasound-directed follicular aspirations between June 1999 and June 2001. Intervention(s): Standard protocol for pituitary down-regulation and ovarian stimulation. Main Outcome Measure(s): Number of oocytes retrieved, embryos transferred, fertilization, and pregnancy rates. Result(s): The numbers of oocytes obtained per cycle were classified into groups A, B, C, and D, consisting of 110, 124, 96, and 122 cycles, with 1-5, 6-10, 11-15, >15 oocytes retrieved from each patient in each group, respectively. The chance of not obtaining a viable oocyte for injection was highest in group A (5.5%). Most fertilization failures occurred in group A (11.8%). Total cleavage failure occurred in the greatest percentage of cycles in group A (3.6%) with a significantly lower mean number of embryos (1.9 +/- 1.7) being transferred. The clinical pregnancy rate was also lowest in group A (7.1 %) compared with groups B (25.8%), C (20.8%), and D (23.8%). Conclusion(s): Retrieval of between 6 and 10 oocytes per patient and transfer of a maximum of three cleavage-stage embryos results in high pregnancy rates. (C) 2003 by American Society for Reproductive Medicine.