P-231 The effect of warming blastocysts in Vitrolife media previously vitrified in Cook media on reproductive potential and clinical outcome

Abstract

Abstract Study question Does the use of a different manufacturer’s media for vitrification and warming of blastocysts affect pregnancy, miscarriage and live birth rates. Summary answer Warming blastocysts in Vitrolife media, previously vitrified in Cook media, does not significantly affect the pregnancy or live birth rate. What is known already Current good practice is to vitrify and warm blastocysts in media manufactured by the same company. This is due to the optimisation of the protocols and media composition intending to maintain high survival rates and associated pregnancy rates. However, circumstances can arise, such as supply and production issues, whereby it is not possible to source the same media for warming vitrified blastocysts as the media they were vitrified in. Study design, size, duration This retrospective cohort study was conducted at TFP-Oxford Fertility. Frozen embryo transfer (FET) cycles included in the study were performed between 2018 and 2022. Embryos that had undergone genetic testing were excluded from the study. The mean women's age was 35 in the control group (Cook warming media) and 36 in the study group (Vitrolife warming media). The average number of embryos transferred was 1.06 vs 1.17 in control vs study group. Participants/materials, setting, methods For the present study 817 patients underwent FET between 2016 and 2018 whereby blastocysts were vitrified in cook media (Sydney IVF Blastocyst Vitrification Kit, K-SIBV-5000) and warmed in cook media (Sydney IVF Blastocyst Warming Kit, K-SIBW-5000). In comparison 704 patients underwent a FET between 2018 and 2022 whereby blastocysts were vitrified in cook media and warmed in vitrolife warming media (Rapidwarm™ Blast, 10120). The pregnancy, clinical pregnancy and live birth rates were compared. Main results and the role of chance Fisher’s exact test was used to calculate the p value and a level of 0.05 was used for significance. The results showed that there was no significant difference in the pregnancy rate, clinical pregnancy rate or live birth rate for blastocysts warmed in Vitrolife media vs Cook media (59.0% vs 57.0% p = 0.56, 47.2% vs 43.9% p = 0.44, 39.3% vs 37.0% p = 0.72) Limitations, reasons for caution This is a retrospective study at a single centre. The number of previous treatment cycles per couple was not included in the study. The study only looked at a comparison of Cook and Vitrolife warming media, no other commercially available media was tested. Wider implications of the findings Although good practice to vitrify and warm blastocysts in the same manufacturer media, our results show that the reproductive potential and clinical outcome may not be adversely affected by using a different manufacturer’s media. However, composition of the media and protocol should be considered and further studies should be conducted. Trial registration number not applicable