Thanks to the embryo freezing and thawing method, which has been applied in IVF Laboratories for 20-25 years, and new techniques developed in recent years, it is possible to achieve a much higher rate of pregnancies. The reason for this is that with the freezing technique, there is a chance to transfer several times (in vitro fertilization trial) from the eggs collected once for the couple, thus increasing the total pregnancy rate. The first frozen embryo baby in the world was born in 1984.
Embryos can be frozen at all developmental stages. Embryos are mixed with a protective liquid and placed in glass tubes and stored frozen at -196 degrees in liquid nitrogen. When frozen embryos are to be thawed, they are removed from liquid nitrogen, thawed at room temperature, separated from the protective liquid, taken into a special culture medium and placed in the incubator. Embryos that look good on the same day can be transferred. We mostly freeze day 3 and day 5 embryos with the vitrification method in our center. After thawing day 3 embryos, we sometimes transfer them on the same day. Sometimes (depending on the characteristics of the patient) we wait 2 days after thawing and transfer the embryos to the 5th day.
Advantages of embryo freezing:
Depending on the patient’s condition, a maximum of 1 or 2 embryos can be transferred in the fresh cycle. If a large number of embryos have formed in the patient, suitable ones are frozen for further use. The probability of survival of embryos after freezing and thawing varies depending on embryo quality, freezing stage, freezing technique, genetic factors and embryo freezing success rates of the center. The probability of survival of frozen embryos after thawing is around 90% in our center. The chance of pregnancy after the transfer with embryos obtained in this way varies depending on the age of the woman.
Conditions where embryo freezing is performed:
– If quality embryos remain after embryo transfer
– If bleeding occurs during treatment
– Depending on the drugs used, all embryos can be frozen, especially in hyperstimulation syndrome (OHSS) developing in patients with polycystic ovaries.
– In cases where the endometrium tissue surrounding the uterus does not thicken enough
– In cases where intrauterine operation is required (endometrial polyp, myoma, adhesion)
– Before cancer treatments that require chemotherapy or radiotherapy
Thawing and transferring frozen embryos provides couples with a chance of almost a fresh trial pregnancy with much less expense. Moreover, there is no need for long-term drug use, egg collection and microinjection processes.
The purpose of preparing the patient for transfer for frozen embryos is to prepare the endometrium and reach sufficient thickness. For this, a natural cycle or a cycle prepared with drugs containing estrogen may be preferred. We follow the ovulation in the natural cycle and wait for the endometrium to thicken on its own. If the day of ovulation is determined and the embryo is frozen on which day, we transfer accordingly. We monitor blood hormone levels (E2, LH, Progesterone) because it is decisive.
We generally prefer the prepared cycle in those who have irregular menstruation and in the advanced age group. Estrogen bands or pills are followed by ultrasound until the endometrium thickness reaches 7-8 mm and we plan the transfer. Pregnancy success is the same with both methods.
Studies have shown that there is no increased risk of anomaly in babies born this way. Scientific studies have shown that frozen embryos give a healthy pregnancy chance even when thawed after a very long time, such as 10-15 years. However, in accordance with the relevant regulation of the Ministry of Health in our country, embryos can be stored for a maximum of 5 years. Legally, spouses must apply with a petition in order to continue the storage of embryos every year. If no application is made at the end of one year, one month is expected and the embryos are legally destroyed.
Preimplantation genetic diagnosis (PGD), on the other hand, is based on the recognition of diseases known to exist and inherited from a single gene. With a different technology called PCR, the change in the gene causing the disease is detected at the embryo level and unhealthy embryos are not transferred.