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.