If you have considered in vitro fertilization (IVF), then you may have questions about what will happen to the extra embryos during the process. If you have extra embryos after the fresh cycle of an in vitro fertilization procedure, then you may choose to have the embryos frozen. This enables you to save the embryos for future attempts at conceiving. Embryos can be cryogenically frozen for up to ten years.



Frozen Embryo Transfer (FET) is considered a non-invasive or minimally invasive type of procedure. Frozen embryos can be thawed and then implanted into your uterus. If you have ovarian or ovulation problems, then FET might be a good option for you when you are considering your infertility treatment options. If you have uterine based problems with carrying out a pregnancy or other disorders, then FET may not be for you. Consult your infertility specialist about what infertility treatments might help you conceive.

Many couples are very concerned with what happens to their extra embryos during an IVF procedure. Educating yourself on how FET works can be very comforting and informative. When pursuing IVF, the man donates sperm and the woman donates eggs. The two are combined in a lab under special environmental and clinical circumstances to create as many embryos (fertilized eggs) as possible. The embryos are studied for viability. The ones that develop the most normally are selected as the ones that will most likely implant. You and your doctor will decide how many embryos to transfer and how many will be cryopreserved.

After viable embryos are chosen, they will be placed into glass tubes. A cryoprotectant is added to the tube. This keeps the embryo safe during the freezing process by not allowing ice crystals to form inside of the embryo. The embryos and cryoprotectant tubes are placed in a special freezer cooled by liquid nitrogen. They are slowly cooled down to one -196 degrees Celsius.

When you are ready to use your frozen embryos, they will be thawed to room temperature, usually the day before the transfer. The cryoprotectant will be completely washed away during a series of solution soakings. Next, the embryos are warmed up to body temperature and mixed with a solution medium.

Your body will be monitored for optimal implantation timing. Normally, three to four embryos will be transferred at once to increase the chances of implantation. You will need to discuss how many embryos to transfer with your infertility doctor. Your ovarian follicles will most likely be suppressed with medications, and your uterine lining will be developed with other medications. Ultrasounds will help your doctor determine the best time to transfer the embryos.

Embryos are easily transferred through your cervix and directly into your uterus. This is a minimally invasive, only slightly uncomfortable procedure. Your cervix will most likely allow entrance of the transfer catheter without difficulty or pain. You may experience some mild discomfort and cramping during and after the procedure. Success rates depend on your individual condition, so you should discuss your chances of a successful pregnancy through FET with your reproductive endocrinologist before you begin any type of infertility treatment.