Cryopreservation is the process of preserving sperms, excess embryos, blastocysts and more recently oocytes in a frozen state for future retrieval and usage. It requires sophisticated, expensive equipments for the procedure and liquid nitrogen jars for storage. It requires special media formulated for freezing.
Process of cryofreezing:
The oocytes, embryos or sperms are initially exposed to cryoprotective agents in order to dehydrate them, followed by loading into straws, slow cooling and finally plunging into a temperature of – 196°c in liquid nitrogen where it can be preserved indefinitely.
Cryopreservation is very useful for those patients who have hyperstimulation syndrome and have excess oocytes or embryos requiring storage for future use. It is also used for the male partner to freeze semen samples ahead of the procedures giving them flexibility where jobs are concerned.
Cryopreservation of eggs have become a reality to preserve fertility and have a biological child at a later date.
Who is a candidate for freezing their eggs?
- Women who would like to delay their pregnancy
- Women who are about to undergo chemotherapy/ radiotherapy for cancer
- Women who have a high likelihood for premature ovarian failure
- Women who object to storing of frozen embryos due to religious beliefs
When is the ideal time to freeze the eggs?
There is no such ideal time . Any woman who is going to delay her pregnancy and is around 35 years of age is an ideal candidate for egg freezing.
How long can the eggs remain frozen?
There is no scientific evidence to show that frozen eggs decrease in quality over time.This means that embryos can be frozen for how ever long necessary.
How many eggs to ideally freeze?
Egg thaw rates are 75% ( 25% of the eggs may not survive thawing process). And 80% fertilization rates are expected for woman around 35 years of age.
So if 10 eggs are frozen , 7 are expected to fertilize .Three to four embryos will be transferred per cycle. So 10 eggs will be ideal for two cycles.
Is egg freezing safe?
The largest published study of over 900 babies from frozen eggs showed no increased rate of birth defects when compared to the general population. Additionally, results from one study showed no increased rates of chromosomal defects between embryos derived from frozen eggs compared to embryos derived from fresh eggs. In 2014 a new study showed that pregnancy complications were not increased after egg freezing.
Sperm Freezing via cryopreservation enables preservation of fertility for an indefinite period of time. The cryopreservation does not affect the quality of the sperm in any way and are similarly potent as fresh samples. We also freeze ahead of procedures in those whom a collection problem is anticipated or for using pooled samples in case of male factor.
Who is a candidate for sperm freezing?
- Men who are about to undergo chemotherapy/radiotherapy for cancer.
- Men who are about to undergo testicular surgery
- Men who are unavailable during the ICSI/IVF treatment cycle