Comparison of embryo quality between intracytoplasmic sperm injection and in vitro fertilization in sibling oocytes

BACKGROUND: The aim of the present study was to compare the quality of embryos derived from sibling oocytes by in vitro fertilization (IVF) or ICSI. METHODS: Consecutive patients with a less than 40% fertilization rate in a previous standard IVF cycle or with relative male factor infertility were recruited for the study. The oocytes retrieved from each patient were divided into two groups for either conventional insemination (group A) or ICSI (group B). Power analysis showed that to detect a 25% difference in the rate of high-quality embryos between the groups with a power of 0.8, at least 1,200 oocytes were needed in each group. RESULTS: One hundred seventy-seven patients were included in the study. Group A was comprised of 1,526 oocytes and group B of 1,480 sibling oocytes. As expected, the fertilization rate was significantly higher in group B than group A (67.1 vs. 43.6%, p < 0.001). No significant between-group differences were observed in cleavage rate (92.7 and 89.7%, respectively) and the rate of either grade A embryos (22.6 and 23.9%, respectively) or grade A(1) embryos (37.3 and 33.5%, respectively). However, in the subgroup of patients with relative male-factor infertility (n = 36), the rate of grade A(1) embryos was significantly higher in the IVF than the ICSI group (46.4 vs. 29.0%, respectively, p = 0.02). CONCLUSIONS: Embryo quality does not seem to be influenced by the mode of fertilization (IVF or ICSI). We assume that embryo quality depends on intrinsic factors of the gametes involved rather than on the fertilization process per se.