Objective: To compare the rates of blastocyst stage development between embryos fertilized after one (MPN) or more than two pronucleus (PN) (3PN, 4PN-multiPN) with those after 2PN in the same patients.
Material and methods: The embryos of patients who had both abnormal PN (MPN, 3PN or 4PN) and normal fertilized (2PN) embryos after intracytoplasmic sperm injection (ICSI) fertilization, were followed with a time-lapse system following the ICSI procedure. The rates of reaching the blastocyst stage were compared between normal and abnormally fertilized embryos.
Results: One thousand eight hundred and twenty oocytes were collected from 140 patients and 1280 (70.3%) of them were fertilized. MPN, 2PN and 3PN, 4PN (multiPN) ratios of the embryos in the pronuclear stage were 11.4%, 83.13% and 5.47%, respectively. The rates of reaching the blastocyst stage among these embryos were 17.1%, 60.8% and 42.8% for MPN, 2PN and multiPN, respectively. The proportion reaching blastocyst development was significantly higher following 2PN compared to those after MPN and multiPN (p<0.05). Embryos developing after multiPN had significantly higher rates of reaching the blastocyst stage compared to those after MPN (p<0.01).
Conclusion: The majority of abnormally pronucleated embryos arrest without reaching the blastocyst stage. MultiPN embryos have a higher rate of blastocyst development than MPN embryos.
Keywords: Blastocyst; ICSI; MPN; multiPN; time-lapse.