Fatty acid supplementation into warming solutions improves pregnancy outcomes after single vitrified‐warmed cleavage stage embryo transfers

PURPOSE: This study aimed to examine the embryonic development of human 4‐cell stage embryos after warming with fatty acids (FAs) and to assess the pregnancy outcomes after single vitrified‐warmed cleavage stage embryo transfers (SVCTs). METHODS: Experimental study: A total of 217 discarded, vitrified human 4‐cell stage embryos donated for research by consenting couples were used. The embryos were warmed using the fatty acid (FA)‐supplemented solutions (FA group) or nonsupplemented solutions (control group). The developmental rate, morphokinetics, and outgrowth competence were analyzed. Clinical study: The treatment records of women undergoing SVCT in natural cycles between April and September 2022 were retrospectively analyzed (April–June 2022, control group; July–September 2022, FA group). RESULTS: Experimental study: The rate of morphologically good blastocysts was significantly higher in the FA group than in the control group (p = 0.0302). The morphokinetics during cleavage, morula, and blastocyst stages were comparable between the groups. The outgrowth was significantly increased in the FA group (p = 0.0438). Clinical study: The rates of implantation, clinical pregnancy, and ongoing pregnancy after SVCTs were significantly increased in the FA group (p = 0.0223–0.0281). CONCLUSIONS: Fatty acid‐supplemented warming solutions effectively improve embryo development to the blastocyst stage and pregnancy outcomes after SVCTs.