Significantly superior response in the right ovary compared with the left ovary after stimulation with follicle-stimulating hormone in a pituitary down-regulation regimen

Objective: To compare the differences between the right and left ovarian responses in patients undergoing standard in vitro fertilization (IVF) treatment. Design: Prospective, observational study. Setting: A university hospital in Taiwan. Patient(s): Seven hundred eighty-nine consecutive patients undergoing IVF or intracytoplasmic sperm injection. Intervention(s): None. Main Outcome Measure(s): The number of oocytes retrieved, fertilization rates, number of grade 1 zygotes and number of embryos produced, embryo arrest-free rate, and mean number of top-quality embryos on the day of transfer. Result(s): The number of follicles ≥16 mm in diameter on day 2.5 versus 2.2 of human chorionic gonadotropin (hCG) administration, the number of follicles ≥10 mm in diameter on hCG day 6.5 versus 6.1, the number of oocytes (3.6 vs. 3.0), the percentage fertilization (79.9 vs. 74.6%), and the mean number of mature oocytes and grade 1 zygotes (2.3 vs. 1.8 and 1.79 vs. 0.93, respectively), and the mean available number of top-quality embryos on transfer day 1.39 versus 0.73 were all statistically significantly greater in the right compared with the left ovary; however, the pregnancy and implantation rates were similar. Conclusion(s): There are statistically significant differences between the right and left ovarian responses in IVF patients with healthy ovaries, and the right ovarian responses are superior to the left ovarian responses.