Late intracytoplasmic sperm injection in unexpected failed fertilization in vitro: diagnostic or therapeutic?

Objective To evaluate fertilization potential of 24-hour-old unfertilized oocytes using intracytoplasmic sperm injection and the pregnancy potential of resultant embryos. Design: Prospective observational study. Setting Private infertility clinic, London, United Kingdom. Patients Fifteen patients with a history of infertility who underwent treatment with IVF and showed failure of fertilization on the day after oocyte retrieval. Intervention Assisted fertilization with intracytoplasmic sperm injection was carried out at 24 hours after oocyte retrieval. Results A total of 121 metaphase II oocytes were subjected to intracytoplasmic sperm injection. Of these, 9 were damaged (7%), 2 were polyploidic (2%), and 58 showed normal fertilization (48%). Of the latter, 47 cleaved normally (81%). Forty embryos were transferred and three were cryopreserved. One patient conceived (7%) but in this case only one of three embryos transferred was from intracytoplasmic sperm injection. Conclusion Late (24 hours) intracytoplasmic sperm injection can give good fertilization and cleavage rates but the potential of the generated embryos to achieve pregnancy seems to be low.