BIRTH OF HEALTHY BABIES FROM BLASTOCYSTS DERIVED FROM MONO-PRONUCLEAR ZYGOTES FOLLOWING INTRACYTOPLASMIC SPERM INJECTION

Abstract

We have previously reported that 80.7% of 1PN zygotes derived from IVF or ICSI had a biparental chromosome, and some of these developed to the blastocyst stage (Tokoro et al. ASRM 2013). However, it has also been demonstrated that all embryos derived from 1PN-ICSI zygotes are chromosomally abnormal and these zygotes should be discarded, though 1PN zygotes derived from IVF(1PN-IVF) could be used for reproductive purposes (Mateo et al. Fertil Steril. 2013; 99: 897-902). In addition, it has been reported that zygotes derived from 1PN-ICSI produced blastocysts but did not lead to pregnancies (Igashira et al. ASRM 2016). In this study, we examined mono-pronuclear zygotes derived after ICSI (1PN-ICSI) can develop normally and result in a healthy live birth. Retrospective cohort study This was a retrospective study including 2482 ART patients treated in 2814 cycles and where 3618 zygotes formed 1PN after ICSI. The time period was 72 months (January 2013 to December 2018). Patients seeking infertility treatment in a well-established private IVF clinic. Blastocyst rates, clinical pregnancy and miscarriage rates after a single blastocyst embryo transfer following the culture of 1PN-ICSI zygotes were compared with data on 1PN-IVF or normal 2PN zygotes during the same time period. Furthermore, follow up information was obtained on the health status of live births derived from 1PN-ICSI zygotes. Statistical significance was determined using the chi-square test (level of P<0.05). The formation rate of 1PN-ICSI was 2.8%(3618/127728), significantly lower (P<0.05) than 1PN-IVF (4.6%; 1044/22799). The blastocyst rate of 1PN-ICSI zygotes (14.8%; 525/3547) was significantly lower (P<0.05) compared to 1PN-IVF zygotes (26.5%; 274/1035) or normal 2PN (62.0%, 22420/36189) . The clinical pregnancy rate of 1PN-ICSI transferred zygotes (24.4%; 53/217) was significantly lower (P<0.05) compared to 1PN-IVF transferred zygotes(36.6%; 41/112) or normal transferred zygotes from 2PN (40.2%; 4802/11947). However, the miscarriage rates were not significantly different (respectively, 30.2%, 34.1% and 23.3%) 21 healthy newborns were obtained from the successful pregnancies after embryo transfer of 1PN-ICSI blastocysts. These results suggest that not all 1PN-ICSI zygotes are abnormal, and these can result in a viable pregnancy and healthy live birth. Continued culture to blastocyst of 1PN-ICSI zygotes should be carried out in order to further assess their potential for transfer.