Associations between the average blastomere number of all embryos on day 3 and the live birth rate in the transfer cycle: a single-centre, retrospective study

Abstract

Abstract Research question: What are the influencing factors of the average blastomere number of all embryos in D3 patients and the association with a live birth rate in the transfer cycle? Methos: A total of 7420 fresh embryo transferred cycles of patients who underwent IVF-ET in the Reproductive Medicine Center, Renmin Hospital, Hubei University of Medicine from January 2016 to December 2021 were selected retrospective observed. Results: According to the average blastomeres number in all embryos on day 3 following oocyte retrieval, the patients were split into five groups: 5.00 group (747 cases), 5.01-6.00 group (1763 cases), 6.01-7.00 group (3052 patients), 7.01-8.00 group (1646 cases), and >8 groups (212 patients). The average number of blastomere on D3 was negatively associated (P <0.05) with infertility, duration infertility, male factors infertility, E2 value on hCG day, and ICSI insemination method. The live birth rate(LBR) of the groups 5.00 and 5.01-6.00 was considerably lower than that of the other groups, according to multivariate regression analysis（P＜0.001). Further additional curve fitting was utilized to demonstrate that the LBR increased significantly as the number of blastomeres grew, increasing a value of 20% for every different blastomere number when the average number of blastomeres on D3＜5.7 (P<0.001). On the other hand, when the number≥5.7 (P=0.258), the live birth rate no longer increases. Conclusion: An average blastomere number between 7.01 and 8.00 is associated with higher LBR in D3 fresh embryo transfer cycle, when the average blastomeres in D3 embryos are less than 5.7 to reduce the live birth rate of the transfer cycle.