Today, embryo freezing is seen as an integral part of assisted reproductive treatments. Freezing embryos is a great convenience for couples who will undergo in vitro fertilization treatment.
In this context, after the embryo transfer process is performed, the remaining embryos are evaluated by embryologists. If they are determined to be suitable for the freezing-storage process, the freezing-storage process is carried out depending on the written consent of the couple.
Thus, embryos with live and good characteristics are not discarded. In the possible trial of the couple at a later time, there is a chance of pregnancy without the need for egg collection again.
Since the embryo freezing process is to prepare the ground for pregnancy, high-quality embryos that are determined to have a high chance of becoming pregnant are frozen.
Freezing embryos that have no chance of becoming pregnant when thawed is not preferred. In another method, fresh embryo transfer is not done consciously and good embryos are directly frozen, the uterus is prepared in the planned cycle and the transfer is made.
How is Embryo Freezing Done?
The process of balancing and cooling embryos with chemical substances called cryoprotectants, storing them in liquid nitrogen at -196 degrees Celsius, removing them from the cryoprotectant environment after the thawing process, and placing them in special culture environments to ensure their further development is called embryo freezing and thawing.
Embryo freezing is a process that can be technically applied at all stages of embryo development.
The probability of embryo loss in a successful freeze-thaw process is very low today.
In Which Cases Are Embryos Frozen?
If there is a large number of high-quality embryos left after the embryo transfer, the embryo can be frozen with the patient’s consent in order to be used again at other times if needed. If IVF treatment is required again in the future, ready embryos are used without the need to complete the egg creation and egg collection processes again. The fact that the expectant mother does not receive ovulation stimulating treatment again and does not undergo egg collection is considered a financial and physical advantage.
In case of excessive stimulation of the eggs, namely Ovarian Hyperstimulation Syndrome, the transfer is canceled since continuing IVF treatment is risky. The embryos are frozen and stored, and when the condition improves, the embryos are thawed and the transfer procedure is performed.
In cases where the endometrium, namely the inside of the uterus, is not suitable for the mother, it is more appropriate to postpone the embryo transfer. In this case, the embryos are frozen and stored, and the thawed embryos are used after the uterine lining is thickened.
In patients who have a risk of damage to their ovaries due to treatments such as chemotherapy and radiotherapy and not being able to obtain eggs in the future, the embryos can be frozen for use in the future.
How Are Thawed Embryos Transferred?
Before the transfer of thawed embryos, the mother’s uterine lining is prepared with menstruation. This preparation process is carried out with natural cycles or estrogen-containing drugs. In the natural cycle, the patient’s follicle is monitored and the endometrium is expected to thicken on its own, and the timing of ovulation in the developing follicle is ensured by administering a rupture injection.
During this process, the patient’s blood hormone levels are monitored. After the thawed embryos are transferred, hormone support treatments continue.
Estrogen-containing patches or pills are used in the prepared cycle. The uterine thickness and hormonal changes in the blood are monitored with ultrasound. Approximately on the 16th-18th day of the menstrual cycle, the endometrium thickness and hormonal status are evaluated. If suitable, the embryos are thawed and the transfer procedure is performed.
