Optimal timing for oocyte denudation and intracytoplasmic sperm injection

Objectives. To analyze the impact of oocyte denudation and microinjection timings on intracytoplasmic sperm injection (ICSI) outcomes. Study Design. We included ICSI cycles with the following parameters: rank 1 or 2, female age <36 years, male factor infertility, long protocol using GnRH agonist and rFSH for ovarian stimulation, and use of freshly ejaculated sperm (n = 110). Several ICSI parameters were analyzed according to the time between oocyte retrieval and denudation (T(1)) and the time between denudation and ICSI (T(2)) using a statistical logistic regression analysis. Results. Neither T(1) nor T(2) had a significant influence on the Metaphase II (MII) rate but the fertilisation rate (FR) showed a significant improvement when T(1) was longer (optimal results at T(1) = 3 hours) while FR significantly decreased with the increase of T(2). Optimal implantation (IR) and pregnancy (PR) rates were obtained when T(1) was around 2 hours. Conclusion. Incubation of oocytes around 2 hours between retrieval and denudation may not increase MII rate but appears to lead to the optimal combination of FR and IR.