Hindawi Publishing Corporation Obstetrics and Gynecology International Volume 2012, Article ID 403531, 7 pages doi:10.1155/2012/403531 Research Article Optimal Timing for Oocyte Denudation and Intracytoplasmic Sperm Injection Catherine Patrat, 1 Aida Kaffel, 2 Lucie Delaroche, 1 Juliette Guibert, 3 Pierre Jouannet, 2 Sylvie Epelboin, 4 Dominique De Ziegler, 5 Jean-Philippe Wolf, 2 and Patricia Fauque 6, 7 1 Laboratoire de Biologie de la Reproduction, AP-HP, Hˆ opital Bichat Universit´ e Paris Diderot, 46 Rue Henri Huchard, 75018 Paris, France 2 Laboratoire de Biologie de la Reproduction, AP-HP, Hˆ opital Cochin, 75014 Paris, France 3 Service de Gyn´ ecologie-Obst´ etrique, Institut Mutualiste Monstsouris, 75014 Paris, France 4 Service de Gyn´ ecologie-Obst´ etrique II, AP-HP, Hˆ opital Bichat, 75018 Paris, France 5 Service de Gyn´ ecologie-Obst´ etrique II, AP-HP, Hˆ opital Cochin, Universit´ e Paris Descartes, 75005 Paris, France 6 Laboratoire de Biologie de la reproduction CECOS, CHU de Dijon, Universit´ e de Bourgogne, Dijon, France 7 Institut Curie, CNRS UMR 3215, INSERM U934 Paris, France Correspondence should be addressed to Catherine Patrat, catherine.patrat@bch.aphp.fr Received 20 July 2011; Revised 8 November 2011; Accepted 20 November 2011 Academic Editor: Neeta Singh Copyright © 2012 Catherine Patrat et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 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. 1. Introduction Intracytoplasmic sperm injection (ICSI) is the treatment of choice for couples with severe male infertility. The micro- injection technique has been completely standardized but there is no common standard for the precise timings of all the procedures. No more than 7 studies focusing on the influence of ICSI procedure timings on the outcoming results were published [1–8], with discrepancies in the conclusions. Although it has been shown that incubation of oocytes for 2–6 h prior to IVF (In Vitro Fertilization) improves fertilization and pregnancy rates [9–12], there are some con- flicting results regarding the timing of ICSI. It has been re- ported that a preincubation period between oocyte retrieval and injection in ICSI cycles improved the percentage of mature oocytes [5, 6], the fertilization rate [1, 6, 7], and the embryo quality [1, 2]. A long oocyte preincubation (9– 11 hours) prior to ICSI is thought to have bad effects on embryo quality [2], probably due to oocyte ageing. How- ever, other studies supported different results as no statisti- cally significant differences in the fertilization [3, 4] or the pregnancy rates [2, 6] were found in preincubated oocytes during ICSI cycles. In theory, some problems may be associated with the in- jection time. Oocytes are retrieved prior to ovulation in the procedure of IVF or ICSI. According to some reports [13, 14], preovulatory oocytes are not fully mature, even though a first polar body is present. It is so called the cytoplasmic immaturity. Cytoplasmic maturity is thought to be asynchronous with nuclear maturity in stimulated cycles