[Increasing the cumulative live birth rate : low-grade blastocysts, potential overlook].

It is now widely recognized that, following prolonged culture, the transfer of a high-quality morphologically graded blastocyst is the preferred strategy in embryo transfer. Low-grade blastocysts are often considered to have a low implantation potential, and their use remains highly limited. We conducted a general review of the literature, including publications from August 2017 to October 2023, to assess the current state of knowledge regarding these embryos, which are generally excluded in routine practice. Our primary outcome measure was the "live birth rate" following the frozen transfer of a low-grade morphologically classified blastocyst according to the Gardner classification. The "miscarriage rates" were also evaluated. Low-grade blastocysts can result in live births, with rates ranging from 5.9% to 40%, and in the birth of healthy children, which remains the primary goal of Assisted Reproductive Technology. It would therefore be relevant to reconsider the routine use of these embryos.