Maximum 2 embryos can be transferred to a patient. If more than one embryo has been achieved with the patient, convenient embryos of remaining ones can be frozen for later use. So, even if a pregnancy has been achieved or not, the patient will have a second chance for pregnancy through frozen embryos.
The next cycle will be easier, cheaper and less tiring because the patient has not undergone an ovarian stimulation and egg collection. Once the embryos have been frozen, they can be stored up to 5 years. If one wishes to store the embryos more than 5 years then a ministerial permission will be required. If the patient is no longer able to provide embryos, this period can be extended.
Survival of embryos after freezing and thawing varies depending on the quality of embryo, freezing phase, freezing technique, genetic factors, and the center’s success rate of freezing the embryos. The possibility of survival of frozen embryos is around 70% after thawing. The chance of pregnancy achieved by transferring such embryos varies depending on the age of woman.
Embryos are frozen using various methods such as slow and fast freezing, and vitrification. Freezing process is decided by evaluating many factors such as patient history, and number and quality of embryos. Frozen embryos are stored in special tanks with -196 ºC containing liquid nitrogen. Written and oral consent of either of the couple is required for freezing and thawing procedure.
When the patient requests to use her frozen embryos, she will undergo an easy preparation process to prepare intrauterine tissue (endometrium) of the patient then the embryos will be thawed. The best quality and living embryos that are still in division progress are placed into the uterus of future mother by means of a catheter. The next process is the same as in the trial of test tube baby.
This method is successfully performed at our center as it is cheaper and easier and also existing embryos are used.