Cumulative live birth rate and neonatal outcomes after early rescue ICSI: a prop

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Yaping Jiang†, Lei Jin†, Bo Huang   , Li Wu, Xinling Ren, and Hui He 

ABSTRACT
STUDY QUESTION: Is early rescue ICSI (E-RICSI) an effective and safe technique compared to conventional ICSI?
SUMMARY ANSWER: Despite the higher multi-pronucleus (PN) rate compared to conventional ICSI, E-RICSI did not add extra risks to clinical and neonatal outcomes.

WHAT IS KNOWN ALREADY: Based on the finding that the second polar body was released in 80% of fertilised oocytes by 4h after exposure to spermatozoa and in 90% of fertilised oocytes by 6h, E-RICSI brings forward the timing of rescue ICSI to 6h after initial insemination and effectively prevents oocyte ageing and embryo-uterus asynchrony. However, some researchers still voice concerns about the efficacy and safety of E-RICSI, and comparative studies are limited.
STUDY DESIGN, SIZE, DURATION: A retrospective cohort study was conducted on patients who underwent conventional ICSI or E-RICSI treatment between January 2015 and December 2020 at a university-affiliated hospital. Using 1:1 propensity score matching, 1496 cases entered each group.

PARTICIPANTS/MATERIALS, SETTING, METHODS: In total, 1496 couples undergoing conventional ICSI oocyte retrieval cycles and 1496 undergoing E-RICSI oocyte retrieval cycles were enrolled in this study, and basic clinical characteristics, embryologic data, clinical outcomes and neonatal data were compared between groups. The embryos in the E-RICSI group were divided into two subgroups: those fertilised by IVF (IVF subgroup) and those fertilised by E-RICSI (E-RICSI subgroup). The embryologic data, clinical outcomes, and neonatal data for these subgroups were also compared with those of the conventional ICSI group. Logistic regression was used for statistical analysis with potential confounder adjustment.

MAIN RESULTS AND THE ROLE OF CHANCE: The 2PN rate, blastocyst formation rate, and viable blastocyst formation rate of the E-RICSI group were significantly lower compared to the conventional ICSI group (2PN rate: P<0.001; blastocyst formation rate: P<0.001; viable blastocyst formation rate: P¼0.004), and the multi-PN rate in the E-RICSI group was significantly higher than the conventional ICSI group (P<0.001). However, the numbers of 2pn embryos, normal cleavage embryo rates, Day 3 high-quality cleavage embryo rates, and high-quality blastocyst rates were similar between groups. When considering the IVF embryos and E-RCSI embryos in the E-RICSI group independently, the 2PN rate of the conventional ICSI group was significantly lower than E-RICSI subgroup but higher than the IVF subgroup, whereas the blastocyst formation rate and viable blastocyst formation rate were higher than E-RICSI embryos but comparable to IVF embryos. Regarding the clinical and neonatal outcomes, the implantation rate in the E-RICSI subgroup was significantly lower than in the IVF subgroup but comparable to that in the conventional ICSI group. Conversely, the low birthweight (LBW) rate was significantly lower compared with the conventional ICSI group but similar to that in the IVF subgroup. No other differences were observed among the three groups for cumulative clinical pregnancy rate, cumulative live birth rate, and the pregnancy outcomes per transfer, including clinical pregnancy, ectopic pregnancy, miscarriage, and live birth, either in fresh or frozen embryo transfer cycles. Furthermore, neonatal outcomes, including cesarean section, sex ratio, LBW, preterm birth, and macrosomia, were similar among groups.

LIMITATIONS, REASONS FOR CAUTION: This study is limited by the retrospective design, limited sample size, and short follow-up period. However, our study underlies the need for large-scale, multi-center randomized controlled trials with long-term follow-up.

WIDER IMPLICATIONS OF THE FINDINGS: Short-term insemination (3h) combined with E-RICSI may be a safe and effective method to prevent the occurrence of total fertilisation failure, and patients with normal or borderline sperm could be encouraged to try IVF first.