Frozen Embryo Transfer or Cryo-preserved Embryo Transfer Procedure
Cryopreserved embryo transfer is a procedure that follows various stimulation for egg retrieval, embryo development, and culture. The egg is first fertilized, and the embryo is then frozen and preserved. The frozen embryo, when needed, is then thawed while we prepare the uterus for embryo implantation with hormonal supplementation using estrogen and progesterone.
The embryo is transferred while the recipient is awake, as this is a painless procedure. A flexible catheter is inserted through the cervix into the uterus under ultrasound guidance. Due to the curve to reach the uterine cavity, sometimes there are chances of slight obstruction, which is easily handled by the physician, and during this obstruction, ultrasound helps to guide the physician to reach the correct site.
A gentle embryo transfer is essential as an embryo, which is gently done without any bleeding, has higher chances for pregnancy, and it’s very necessary for the physician to use ultrasound to guide him for implanting the embryo.
Types of cryopreserved embryo transfer
- fresh IVF embryo transfer
- Frozen embryo transfer
The follicles are stimulated to retrieve the egg for in vitro fertilization. If the fertilized embryo is implanted in the patient in the same cycle, then it is known as Fresh embryo transfer.
Alternatively, we can freeze the embryo and can plan for transfer in the future cycle; this procedure is known as frozen embryo transfer. Of course, in the forthcoming cycle, the patient will only undergo the embryo transfer process and not ovarian stimulation or egg retrieval.
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Indications for frozen egg transfer
Fresh embryo transfer was earlier believed to have better pregnancy results, but some studies later broke this myth. Frozen embryo transfer has a better pregnancy outcome when compared to fresh embryo transfer.
Other indications
- For excess embryo from a fresh transfer. For example, if during IVF, there is more than one healthy embryo, the rest of the embryo is frozen for later use.
- Suppose the recipient has a high response to ovarian stimulating medication. In these cases, we prefer to freeze the embryo to prevent hyperstimulation syndrome during pregnancy.
- To delay pregnancy. If the recipient is not ready to plan pregnancy, then, the embryos are frozen and are implanted according to the ease of the recipient during any future cycle.
- Genetic testing for the embryo. If some genetic testing needed before transferring the embryo, the embryos are frozen. These genetic tests are mainly to rule out any genetic disorder in the embryo.
How are the embryos frozen
The embryo is frozen through vitrification or extra rapid cooling of the embryo to prevent ice chunks. This process of Cryopreservation has improved the survival rates of the embryo by up to 90 percent when compared to the older methods of freezing embryo.
When the embryo is frozen, it is stored indefinitely in liquid nitrogen. When the recipient is ready for transfer, these embryos are thawed and will undergo frozen embryo transfer.
What’s the procedure for it?
Mr. DJ, Thank you for posting your query. Please note the procedure for frozen embryo transfer-
Five days after fertilization when the fertilized cells reach the stage of blastocyst it is frozen and preserved. When the recipient is ready to undergo pregnancy the frozen blastocyst is thawed and is made ready to implant in the women on the same day.
To make sure that the lining of the embryo matches with that of the uterus so progesterone is administered to the women for 5-6 days before transplanting the embryo.
The embryo is transplanted by the embryologist through a catheter. Transvaginal ultrasonography is done to guide the embryologist to help him reach the exact place through the cervix into the uterus. As soon as the tip of the catheter reaches the exact spot the embryologist carefully deposits the embryo. Transplantation of the embryo is then confirmed by the doctor.
Due to any reason which is quite rare that if the embryo cannot be reached to the uterus through the cervix then it is placed by giving an incision in the abdomen.
The procedure of embryo transfer does not need anesthesia and the recipient of the embryo can be sent back home within 3-4 hours after the transplant.