P-472 Endometrial stimulation with culture medium containing granulocyte macrophage colony-stimulating factor promotes embryo implantation after vitrified-warmed blastocyst transfer

Abstract Study question Does endometrial stimulation with culture medium containing granulocyte macrophage colony-stimulating factor (GM-CSF) promote implantation potential of vitrified-warmed blastocysts? Summary answer Endometrial stimulation with culture medium containing GM-CSF prior to transfer of vitrified-warmed blastocysts may promote embryo implantation and improve pregnancy continuation. What is known already Human embryonic development and implantation in vivo is precisely regulated by various cytokines, including growth factors. GM-CSF is a cytokine that plays an important role in reproductive function. We reported the possibility that the use of culture medium containing GM-CSF in cleavage stage vitrified-warmed embryo transfers (ETs) promotes embryo implantation (ESHRE2018). However, it has been reported that endometrial stimulation with culture supernatant up to blastocyst stage (SEET method) improves embryo implantation, but the effect of endometrial stimulation with culture medium containing GM-CSF (G-SEET method) on embryo implantation is not clear. Study design, size, duration This study was conducted at a single in vitro fertilization (IVF) center from June 2020 to February 2022. The G-SEET procedure was performed at each patient’s request. All study participants provided informed consent, and the study design was approved by the ethics committee of IVF Nagata Clinic, Fukuoka, Japan. Participants/materials, setting, methods We examined 702 cycles of vitrified-warmed blastocyst transfer. Warmed blastocysts were incubated in recovery culture for several hours and transferred on day 5 (control group). For the G-SEET method, only culture medium containing GM-CSF was injected into the uterus two days before ET, which was performed as in the control group (G-SEET group). The human chorionic gonadotropin (hCG) positive, clinical pregnancy, miscarriage, and ongoing pregnancy rates were compared between the two groups. Main results and the role of chance Of the 702 cycles of single vitrified-warmed blastocyst transfers, the control and G-SEET groups had 459 and 243 cycles, respectively. The G-SEET group had a higher patient age (37.5±4.2 vs. 36.2±3.8, p