Purpose: To clarify the effect of preincubation of oocytes on the results of IVF and ICSI.
Methods: A total of 176 IVF and 64 ICSI cycles received long protocol ovarian stimulation. The oocytes were incubated for 1-8 h before insemination or sperm injection. Metaphase II (MII) percentage was evaluated in the ICSI arm; fertilization rates, embryo quality, and pregnancy outcomes were analyzed in both IVF and ICSI arms according to the preincubation period duration of oocytes.
Results: The MII percentage of the ICSI arm was significantly lower (P < 0.05) in the group with preincubation period of < 2.5 h. The fertilization rates in groups with preincubation for 2.5-5.5 h were significantly higher (P < 0.001) for IVF. Embryo quality and pregnancy outcomes were not significantly different between the IVF or ICSI arm.
Conclusions: The preincubation of oocytes for at least 2.5 h is beneficial to both IVF and ICSI outcomes by increasing the nuclear maturity of oocytes.