Frozen Embryo Transfer

Frozen embryo transfer is a procedure that uses embryos that have been previously frozen and stored in an embryo bank. During this procedure, the embryos are thawed and transferred into a uterus, with the aim of achieving pregnancy.

The transfer of frozen embryos can be performed as part of an assisted reproduction treatment, such as in vitro fertilisation (IVF). In these cases, embryos are frozen after being created in vitro and then stored for later use. Embryos that have been obtained through egg or sperm donation may also be frozen and stored.

Frozen embryo transfer is an option for people who wish to have children but are not ready for fresh embryo transfer immediately after in vitro fertilisation. It is also an option for those who have already undergone an IVF cycle and have leftover embryos.

Embryos can be frozen for years. Cases have been reported where embryos have survived freezing for up to 25 years.

The quality of the embryos does not change after freezing. The embryo vitrification technique is very safe. The freezing media ensure that the embryos are not damaged and that the survival rate is close to 100%.

No. We only freeze embryos that have the quality to produce a pregnancy. The quality of the embryos is established according to their characteristics and evolution. This quality determines the probability of pregnancy. Poor quality embryos that would not be transferred are not frozen either.

Yes, pregnancy rates are similar to those of fresh transfers. In some cases, these rates are even higher, as the IVF treatment medication can influence the size of the uterus and it is preferable to let it rest and stimulate it independently.

Yes, although stimulation is simpler than for in vitro fertilisation treatment, as the ovaries do not need to be stimulated. Medication is needed to make the uterus grow and make it receptive so that the transferred embryos can continue their evolution inside it and achieve pregnancy.

The pregnancy test is performed approximately 12 to 14 days after the transfer by measuring the beta HCG hormone in the blood.

Embryo transfer is usually performed between the third and fifth day after in vitro fertilisation, when the embryos are at the blastocyst stage. This means that they have completed a number of cell divisions and have formed a mass of cells called a morula. Embryos are at the blastocyst stage when they are between five and six days old.

However, frozen embryo transfer can be performed at any time, as long as the uterus is ready to receive the embryo. In the case of fresh embryo transfer, the exact date will depend on the growth rate of the embryos and the hormonal response of the woman’s body.

It is important to keep in mind that embryo transfer is only one part of the assisted reproduction process. Before the transfer, a series of tests and treatments are necessary to prepare the woman’s body to receive the embryo and to maximise the chances of pregnancy. These treatments may include medications to stimulate ovulation and control the menstrual cycle, as well as tests to assess the health of the uterus and ovulation.

Embryos are thawed just prior to transfer. The thawing process is carried out carefully to minimise the risk of damaging the embryo.

The first step is to remove the embryo from the freezer and place it in a specially formulated thawing solution. The solution contains a warm saline solution and a substance called trisodium citrate, which helps preserve the integrity of the embryo’s cells during the thawing process.

The embryo is placed in the solution for a few minutes, then removed and placed in a fresh solution of trisodium citrate. The embryo is then examined under a microscope to assess its viability. If the embryo is in good condition, the embryo is transferred.

Embryo thawing and transfer is usually carried out in an assisted reproduction clinic under the supervision of a team of specialised medical professionals.