Analysis of reproductive outcomes in cases with repeated high proportion of multiple pronuclei (MPN) after previous IVF and subsequent ICSI

Intracytoplasmic sperm injection (ICSI) is beneficial for most women with a high multiple pronuclei (MPN) incidence from previous conventional in vitro fertilization (IVF). Nevertheless, a small group of patients still undergo the same problem in the subsequent ICSI treatment. In this research, we aimed to explore whether ICSI is still effective in improving embryonic development and reproductive outcomes in such patients. A prospective cohort study was performed between January 2017 and December 2023, including 12 couples with a high proportion of MPN zygotes in previous C-IVF and subsequent ICSI cycles. The MPN rate was not less than 50% and the number of MPN zygotes was not less than 3 in each initiated cycle for the couples included in the study. We observed no significant differences in the 2PN (22.29 versus 25.14%; p  = 0.526), MPN (45.14 versus 40.98%; p  = 0.427) and 1PN (3.43 versus 2.73; p  = 0.703) rates between previous IVF and subsequent ICSI cycles. After conventional IVF, a total D3 good quality embryo rate of 0% (0/39) was achieved, which was significantly lower than that of 23.91% (11/46) after ICSI (0 versus 23.91%; p  = 0.012). There was no significant difference in the D3 available embryo rate between the two groups (38.46 versus 60.87%; p  = 0.066). ICSI cycles demonstrated significantly lower blastomere multinucleation rate compared with previous IVF cycles (65.21 versus 87.18%; p  = 0.037). We also observed that ICSI showed a significant improvement in the ongoing pregnancy (62.50 versus 0%; p  = 0.031) and live birth (62.50 versus 0%; p  = 0.031) rates compared with conventional IVF. We further identified a novel heterozygous missense mutation of TUBB8 (c.33G > T [p.Q11H]) that cause a repeated high proportion of MPN zygotes. For patients with high proportion of MPN zygotes in previous C-IVF and subsequent ICSI cycles, ICSI still can improve embryo development and reproductive outcomes compared with C-IVF.