Fertilization and neonatal outcomes after early rescue intracytoplasmic sperm injection: a retrospective analysis of 16,769 patients

Purpose To evaluate the efficacy and safety of short-term insemination and early-rescue intracytoplasmic sperm injection (ICSI), an approach that rescued oocytes with unclear second polar body 6 h after initial insemination by ICSI (early R-ICSI) to avoid total or near-total fertilization failure in conventional in vitro fertilization (IVF). Methods We performed a retrospective study in 16,769 patients (short-term IVF, n = 12,094; ICSI, n = 3452; early R-ICSI, n = 1223) who received IVF/ICSI treatment in our hospital from January 2009 to October 2018. Fertilization and clinical outcomes were compared among those three groups. Results When considering the R-ICSI embryos in the early R-ICSI group independently, the rates of fertilization and day-3 cleaved embryos in 2PN oocytes were comparable, the rates of fertilization (2PN) and high-quality embryos were lower, whereas the multi-PN fertilization rate (3.27%) was significantly higher than the ICSI group (1.26%). The difference of clinical pregnancy rate between the part of transferred R-ICSI embryos (40.81%) and the ICSI group (44.73%) remained nonsignificant. Furthermore, the rate of congenital birth defects in the early R-ICSI group (0.99%) was not significantly different from those in the short-term IVF (0.76%) and ICSI groups (1.07%). Conclusion Despite the multi-PN fertilization rate, our study highlights early R-ICSI as a safe and effective alternative in assisted reproduction to decrease complete IVF fertilization failure and reduce ICSI utilization. Additional large amount and long-term follow-up studies are needed to further validate the use of early R-ICSI.