Can the Presence of One Pronuclear Zygote in Fresh Intracytoplasmic Sperm Injection Cycles Provide A Prognostic Factor?

Gilat Sacks Odelya Zaken Nava Dekel Tzurit Eliassian Yaara Cohen-Hadad Henny Mozes Esther Rubinstein Aharon Peretz Ido Ben-Ami Oshrat Schonberger
Ivf, Shaare Zedek Medical Center, Israel

Introduction:
Normal fertilization in early embryo development is crucial for pregnancy outcome.Normal fertilization is defined by the presence of two pronuclear(2PN)in the zygote.When irregular fertilization is observed and more than 2PN are present,the golden standard protocol is to discard the zygotes.When less than 2PN are observed the protocol is unclear, with a debate over use of one pronuclear(1PN)transferred embryos.

The standard use of time lapse incubation,has created a reality where all zygotes(irrespective of their fertilization outcome)remain in the culture-dish,raising more awareness to this debate.

Aim:
Evaluate the outcome of ICSI cycles with at least one 1PN zygote and explore it’s effect on pregnancy rates as a prognostic tool.

Materials Methods:
A two-year(2020-2021)retrospective analysis of all ICSI cycles with at least one 1PN zygote fertilization,focusing on outcome of embryos developed from 1PN zygotes.

Results:
2008 ICSI cycles were performed.403(20%)cycles had at least one 1PN amongst the fertilized zygotes.These cycles included 155(38.5%)PGT cycles in which biopsies were performed.Pregnancy rate was 20% per embryo transfer,7.7% of the cycles were 1PN embryo transfers(ET).The clinical pregnancy rate of 1PN ET was 3.8%. 1PN embryos in PGT cycles yielded good quality embryos for biopsy and genetic analysis.

Conclusions:
Our data highlights the high occurrence of 1pn amongst fertilized zygotes from ICSI cycles and low pregnancy rates.In addition,it supports the limited value of transferred 1pn embryos.However,such embryos should be considered for PGT purposes or when no alternative embryos are available.A future comparable study will compare the pregnancy outcome of cycles without 1PN and explore the presence of 1PN as a prognostic tool.