Some people who are having fertility treatment have embryos which are not transferred in their IVF cycle. Find out how your embryos can be frozen for use in later treatment.
Often with In Vitro Fertilization (IVF) or Intracytoplasmic Sperm Injection (ICSI) treatment, there may be some good quality embryos left after embryo transfer. Instead of disposing them, there is the option to freeze them to use in the future.
Not all embryos are suitable for freezing, so only excellent, good and sometimes average quality embryos are selected for freezing. Embryos can be frozen at different stages of their development, from when they are just one cell, two to eight cells, or at the blastocyst stage (day5).
The embryos are placed in a freezing solution containing antifreeze (cold protectors) which helps to dehydrate or extract water from the embryo and protects the cells. These materials protect embryos from damage caused by the formation of ice crystals. Then they are frozen by quick freezing method (vitrification method).
Frozen embryos are stored in liquid nitrogen tanks at -196 degrees Celsius and kept in a cold room. These tanks are monitored for the nitrogen level and according to the quality control, the embryos can safely be stored for many years.
The pregnancy rate after the transfer of frozen embryos is almost the same as that of fresh embryos. Long-term storage in liquid nitrogen has no effect on embryo viability. The survival rate of embryos frozen for several years is similar to that of embryos thawed after only a few months. In addition, there have been no reports of birth defects in children born from embryos that have been frozen for a long time. Experts now know that frozen embryos can survive indefinitely, and so far, the longest time a frozen embryo has been successfully thawed and transferred is 24 years.
Unfortunately, sometimes a very small number of embryos can withstand the freezing process and do not survive during the freezing and thawing process. In some embryos that survive, they may lose one or two cells, but in many cases, the embryo recovers and continues to grow. The embryologist will discuss with you whether the embryo is not suitable for transfer.
The chances of getting pregnant with frozen embryo transfer largely depend on the age of the woman at the time of embryo formation. Women aged 35 or younger have the highest chance of pregnancy. And the survival rate of frozen embryos after the thawing process is more than 95%.
Before freezing the embryo, it is very important that you give your informed consent by signing the relevant consent forms.
The consent form includes:
First, the embryos should be removed from the storage tank and thawed. Then the embryologist and gynecologist transfer the embryo to the woman’s uterus with the help of ultrasound guide. After the stage of embryo transfer and the passing of 36 hours, the mother can continue her daily activities.
The number of transferred embryos depends on the quality of the embryo and the age of the mother. For women under 38 years old, one to two embryos are transferred, and for women over 38 years old, up to three embryos are transferred.