P-155 Reproductive Potential of Metaphase-I (M-I) Intra Cytoplasmic Sperm Injection (ICSI)
Authors: Atared A , Alratrout D , Abukhaled H , Son W  Y , Al shahrani A 
Published: July 2024

Abstract

Study question
To evaluate the reproductive potential of performing ICSI with metaphase-I (M-I) oocytes derived from In Vitro Fertilization (IVF)-ICSI cycles

Summary answer
M-I ICSI oocytes can fertilize and develop into blastocysts, but with low rates and limited efficiency in producing more embryos, highlighting challenges in reproductive outcomes.

What is known already
ICSI for initially immature oocytes undergoing in vitro maturation in IVF cycles is a topic of controversy with varying practices. While it has the potential to increase usable embryos, it may be time-intensive and yield uncertain results. Assessing the maturation status of M-I oocytes multiple times on collection day is challenging. If viable embryos can be obtained after ICSI with M-I oocytes, it simplifies workload management in busy embryology labs for patients with a limited number of mature oocytes. Despite a few reported cases of healthy live births resulting from ICSI with M-I oocytes, their reproductive potential remains inadequately explored.

Study design, size, duration
The study included IVF cycles (n = 929) with both immature and mature oocytes from Jan, 2022-Dec, 2023. Fertilization and blastocyst were assessed based on oocyte maturity.

Participants/materials, setting, methods
The study included IVF-ICSI cycles obtaining at least one immature (Germinal vesicle (GV), M-I) and one mature (M-II) oocyte at oocyte denudation. Analyzing 9,793 inseminated oocytes from 929 women (mean age: 34.0), we divided them into groups: M-II (Group 1: n = 7678), M-I at ICSI (Group 2; n = 835), M-IàM-II at ICSI (Group 3; n = 643), M-IàM-II on day 1 (Group 4; n = 129), and GVàM-II on day 1 (Group 5: n = 508). Fertilization and blastocyst development were then examined.

Main results and the role of chance
Overall, embryos originating from initially immature oocytes exhibited lower cleavage and blastulation rates compared to those from initially mature oocytes (P &lt; 0.05). In Group 2, where ICSI was performed with M-I oocytes, fertilization and blastocyst rates were 23.6% and 16.1%, respectively. However, these rates were significantly lower than in other groups (P &lt; 0.05). In Group 3, where ICSI was performed with M-II oocytes matured from M-I within 2 hours after oocyte denudation, the fertilization rate per oocyte (55.2%) was lower than in Group 4 (75.7%) (P &lt; 0.05). However, the blastocyst rate per 2PN embryo was higher (30.7%) in Group 3 than that of Group 4 (18.0%) (P &lt; 0.05).
The blastocyst rate from the inseminated oocytes was directly associated with oocyte maturation: 29.3% (2250/7678) for in vivo M-II, 14.9% (96/643) for Group 3, 11.6% (15/129) for Group 4, 8.9% (45/508) for Group 5, and 2.9% (24/835) for M-I (Group 2).
There were few pregnancies resulting from fresh transfers with only embryos produced from day 1 M-II oocytes (3/18=16.7%). While there were pregnancies after transferring only embryos generated from M-II matured from M-I on day 0 (4/10=40%), no patients transferred only embryos produced from M-I oocytes.

Limitations, reasons for caution
Despite the study possessing a substantial sample size, limited availability of embryos for fresh transfers arises from the deprioritization of those originating from immature oocytes. Consequently, it is crucial to conduct further research involving frozen embryo transfers and chromosome analysis to determine the efficacy of M-I ICSI.

Wider implications of the findings
Immature M-I oocytes exhibit a blastocyst formation rate of less than 3%. Consequently, these immature M-I oocytes demonstrate very limited developmental potential in progressing to the blastocyst stage, and ICSI for the M-I stage should be re-evaluated.

Trial registration number
Bnoon20240101