Hormonal stimulation, which leads to collection of more eggs and embryos from one cycle, can negatively affect the quality of the endometrium (uterine mucosa) and embryo implantation. Therefore, since 2010, we tend to decrease the number of fresh transfers and prefer cryoembryotransfer – ie transfers of thawed embryos in one of the cycles following to stimulation.
On the chart above, there is a comparison of the success rate of fresh tranfers and 1st frozen embryo transfers – G+ is a positive pregnancy test, ASP+ clinical pregnancy demonstrated by fetal heartbeat, P+ delivery.
- natural cycle transfer is preferred
- we get more than one quality embryo – blastocyst for use
- a PGT embryo examination is planned
- for health reasons fresh transfer is not recommended (polyp, risk of OHSS)
- as with eggs, it is possible to preserve embryos even before radiotherapy or chemotherapy, where there is a risk of damage to the germ cells, which leads to subsequent fertility disorder
- for example, partners plan to leave after stimulation or the patient becomes ill
We keep improving the vitrification techniques, today we have been using the 4th generation of vitrification techniques – the GAVI vitrification automat. Transfers of embryos vitrified to GAVI have 14.2 % more biochemical pregnancies and 21% more clinical pregnancies with fetal heart activity + compared to Cryotop (our results from 2016-2019 presented at the international conference Fertility Vision 2019).