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Blastocyst developmental potential and euploidy Rates of 0PN oocytes versus 2PNs


Oocytes with no indication of pronuclei (0pn) at the time of fertilization assessment are  often discarded. While there is literature to support that embryos from 0pn zygotes are viable for transfer,  there are few studies that analyze the genetic outcomes of these embryos. The aim of the study was to  determine if 0pns are capable of developing into euploid blastocysts compared to 2pns.


Retrospective study 


A total of 55 patients undergoing IVF with ICSI were included in the  study. Female patients ages ranged from 23-41, with a mean age of 33. Oocytes were assessed for  fertilization between 16-20 hours post insemination. Oocytes that showed 0pn and 2pns were cultured  separately until Day 7 and evaluated for blastocyst development. Patients that had no blastocysts derived  from either 0pn or 2pn were excluded from the study. Blastocysts were biopsied and tested for euploidy using NGS. The blastocyst development rate and euploidy rates were compared between 0pn and 2pn  oocytes using an N-1 Chi-squared test. 


The data obtained are depicted in Table 1. A total of 263 0pns and 697 2pns were cultured  until day 7. No significant difference was noted in the blastocyst rate between the 0pn and 2pn groups  (36.5% vs 39.5%, p=0.39). The blastocysts developed from the 0pn contributed 25.6% of the total  blastocyst rate. The 0pn blastocysts showed a 51.7% euploidy rate compared to 61.7% for the 2pn group (p=0.09), which contributed 22.5% of all euploid blastocysts. 

Table 1: Blastocyst and euploidy rates of 0pn and 2pn embryos

0pn  2pn  0pn + 2pn
263  697  960
Blastocysts  96  275  371
Blastocyst rate (%)  36.5% 39.5% 38.6%
Embryos biopsied  89  256  345
Euploid (%)  46 (51.7%) 158 (61.7%) 204 (59.1%)
Aneuploid (%)  34 (38.2%)  68 (26.6%)  102 (29.6%)
Mosaic (%)  6 (6.7%)  20 (7.8%)  26 (7.5%)
No result (%)  3 (3.4%)  10 (3.9%)  13 (3.8%)

ap=0.39; bp=0.09 


The data shows comparable blastocyst and euploidy rates in blastocysts derived from  0pn and 2pn. The 0pns contributed to the total number of blastocysts available for freezing or biopsy with  comparable euploidy rates. This is compelling evidence to support culturing of 0pns to the blastocyst  stage. It is possible that the 2pns were not identified correctly or were not visible at time of fertilization  check, and therefore should be kept in culture as they have the potential to yield euploid blastocysts.





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