BACKGROUND: Total or near total fertilization failure remains inevitable in conventional in vitro fertilization (IVF). The experts searched for the release of the second polar body 6 h after initial insemination, and rescued those oocytes with unclear second polar body by ICSI (early R-ICSI). Studies found that early R-ICSI can effectively decrease complete IVF fertilization failure and excessive ICSI treatment.METHODS: We performed a retrospective study in 16,769 patients (short-term IVF, n=12,094; ICSI, n=3,452; early R-ICSI, n=1,223) 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%).CONCLUSIONS: Despite the multi-PN fertilization rate, our study highlights early R-ICSI as a safe and effective alternative in assisted reproduction to reduce ICSI utilization. Additional large amount and long-term follow-up studies are needed to further validate the use of early R-ICSI.

BackgroundChromosomal mosaicism and aneuploidies are routine phenomena throughout human pre- and post-implantation development. The benefit of implanting mosaicism or aneuploidies is still controversial. The purposes of the study are to investigate the developmental potential of embryos with chromosomally segmental or mosaic abnormalities, and whether precise Next Generation Sequencing (NGS) resolution would reduce the development of an abnormal embryo in preimplantation genetic testing (PGT) cycles.MethodsThe peripheral blood of 17 PGT babies were collected for single nucleotide polymorphism (SNP) array and were compared with trophectoderm (TE) biopsy results at different NGS resolutions.Results76.5% (13/17) of babies’ peripheral blood chromosome analysis was consistent with 10Mb TE biopsies and 58.8% (10/17) of babies’ analysis was consistent with 4Mb TE biopsies. 2 babies who had euploid TE showed abnormal peripheral blood chromosome analysis. 17.6% (3/17) embryos with aberrant TE biopsies produced healthy babies. Although the sensitivity of 10Mb was lower than 4Mb (25% vs. 50%), the specificity (100% vs. 76.9%), PPV (100% vs. 40%) and diagnostic accuracy (82.4% vs. 70.6%) of 10Mb showed better results than 4Mb.Conclusion(s)The chromosomal results between peripheral blood samples and TE biopsies of born babies are not completely congruent. Aneuploid and mosaic embryos have potential to produce healthy babies, whereas normal embryos also have chance to produce babies with chromosomal abnormalities. In spite of low sensitivity of both resolutions, 10Mb has higher specificity, PPV and diagnostic accuracy than 4Mb. It is suggested that TE biopsy be analyzed in both 10Mb and 4Mb resolutions to uncover severely adverse chromosomal aberrations but use 10Mb resolution to guide transfer.Trial registrationThe study was retrospectively registered in the Chinese Clinical Trial Registry (ChiCTR2100042522).