Frozen embryo transfer


A frozen embryo transfer is a technique in which a previously vitrified embryo is transferred to the patient. These embryos come from previous IVF or ICSI cycles in which good quality embryos were left over or in which the transfer was postponed, or they are donated embryos.

Who is it for?

  • Couples that have vitrified embryos from previous cycles
  • Couples who resort to embryo donation
  • Couples who resort to genetic diagnosis with delayed transfer.
  • When certain indicators have altered levels such as high oestradiol and progesterone, endometrial thicknesses above or below optimal values, personal decisions.


endometrial preparation

As in a cycle with fresh embryos, the patient must undergo an estrogen-based endometrial preparation treatment so that the endometrium presents the appropriate thickness on the day of transfer.

embryo thawing

Embryos of good quality from previous treatments remain preserved in liquid nitrogen tanks, at a temperature of -196º C, which allows their qualities to remain intact.


A few hours after thawing, the embryo is transferred to the patient’s uterus. This process is performed following the same procedure as with fresh embryos, so it is completely painless and does not require the patient to be sedated.


Several days after the transfer, a blood test is performed to determine the value of this hormone to control pregnancy.


  • What is the name and what does the freezing technique consist of?
    • o The process is known as vitrification and it is a technique that combines rapid cooling rates with high concentrations of cryoprotectant, allowing a higher survival rates and the subsequent implantation of embryos.
  • Why are pregnancy rates with frozen embryo transfers sometimes better than those with fresh embryos?
    • The hormonal environment in the uterus is very important and it has been seen that sometimes it can affect the uterine implantation. This is the reason why in certain cases a decision is made to postpone fresh transfer and perform a frozen embryo transfer at a later date.
  • Do children born from a frozen embryo transfer have a higher risk associated with having a disorder?
    • According to various studies, children born by this technique do not present greater risks compared to fresh transfers.