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Following earlier studies introducing an IVF-ICSI Split model on couples with unexplained infertility to avoid the scenario of unexplained failed or poor fertilization, PIVET has adopted a high ICSI rate approaching 90%, whereas the general rate among Australian facilities is around 60%. This observational study with retrospective data analysis reports on the IVF±ICSI procedures conducted over the period 2011 to 2019 with follow-up of ensuing pregnancies through 2020. Using autologous oocytes, 2343 women had 3434 IVF±ICSI cycles where 84.5% of women had 88.9% of initiated treatment cycles using ICSI and only 5.3% of women had 4.0% of cycles by IVF. The remaining 10.1% of women utilized the IVF-ICSI Split model for the remaining 7.2% of cycles. It was shown that oocyte fertilization rates were significantly higher for ICSI (p<0.0001), but not significant for women >40 years. The utilization rates of the ensuing embryos were ~45% across all ages with no significant differences across the ages, except for those small numbers of women ≥45 years who had a higher rate from IVF-generated embryos (p<0.0002). Pregnancy outcome were higher from ICSI-generated embryos across the age groups, being especially marked among the younger women <40 years (p<0.0001). Miscarriage rates were lowest for the IVF-generated pregnancies (overall 6.7% vs 22.8%, p<0.0001) but nevertheless the final live birth productivity rates per initiated treatment cycle remained higher from the ICSI-generated pregnancies (56.5% vs 46.3%; p<0.0001). Although this study does not meet the highest standards for EBM, it emanates from a pioneer facility with >40 years of published activity and which practices 90% blastocyst transfers in >90% SET cycles. The study supports a high ICSI rate of almost 90% and an IVF-ICSI Split rate of 10%.

In assisted reproduction treatments (ART), applying the ICSI method for fertilization of oocytes rather than traditional IVF method, is regarded as controversial for two reasons, namely utility and safety. Our study examines an IVF-ICSI Split model for couples with unexplained infertility, where male factor is meticulously excluded and ART is conducted by a strict algorithm, a commitment to blastocyst culture, along with single embryo transfers and a high commitment to cryopreservation. From 242 treatment cycles, 3346 oocytes recovered (13.8 per OPU) were randomly allocated to IVF or ICSI and the fertilization rates standardized to the number of 2PNS arising from each group applying the metaphase II oocyte number identified for the ICSI group, as the denominator for both groups. The fertilization rates were significantly higher overall for ICSI (83.2% vs 65.4%; p<0.0001), being most pronounced for women under 40 years. The resultant embryos had equivalent implantation rates in both fresh ET and frozen (FET) cycles with no significant differences in pregnancy rates, miscarriage rates or live birth outcomes indicating equivalent embryo quality. However, there were significantly higher numbers of ICSI-generated embryos cryopreserved and subsequent FET procedures showed higher live birth rates (21 births vs 6 births; p<0.005) and potential livebirths (214 births vs 104 births; p<0.0001). No congenital fetal abnormalities were detected in any of the 199 babies delivered during the study period to December 2020, neither IVF-generated nor ICSI-generated. Whilst the data strongly favors ICSI, there were 2 women (from 26 with fertilization in one arm only) who demonstrated fertilization only in the IVF arm of the study. We conclude that the IVF-ICSI Split model should be undertaken on all IVF-naïve women with unexplained infertility to determine the appropriate fertilization mode, albeit ICSI will be safely preferred for >90% of cases.

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