Cryopreservation is the process of freezing and storing embryos for transfer later. Freezing of Embryos gives couples the opportunity to try additional cycles of IVF, either after a failed attempt, or a first birth or even after medical treatments such as chemotherapy. In a single IVF cycle, a large number of embryos are sometimes produced. When transferring embryos back into the uterus we try to avoid twin/triplet pregnancy, and therefore more than 3 embryos are rarely transferred. Thus, at the end of a treatment cycle, extra embryos may be frozen and used in the future in case the patient does not conceive or if she returns for treatment again after completing her pregnancy.
Freezing is done with the aid of an embryo freezer and the embryos are frozen in straws and transferred into liquid nitrogen dewars.
Cryopreservation means freezing and this is a commonly used procedure across fertility centres.
First of all, we commonly freeze sperm. This is done in cases where the husband tends to be traveling over a period of time and is not available at the time of IUI or IVF. Sometimes when men have cancer, before chemotherapy we advice them to freeze sperm so that they can save it for later use and in this case we freeze at least two or three or maybe more such sperm samples. Sperm freezing is also done during an IVF procedure as a backup just in case the man is not able to make it at the time of the egg pickup. So these are the instances where we freeze sperm.
We do egg freezing for women, who wish to store their eggs for later use. If they’re planning to delay their pregnancies or planning to delay getting married.
We also freeze embryos very commonly, because we tend to do more frozen embryo transfers and in these cases all the embryos are frozen. Or sometimes we may have done a fresh embryo transfer and there may be extra embryos and in those cases we freeze the embryos too.
Sometimes couples ask us how long, embryos can be frozen or sperms can be frozen.
They can be frozen for any length of time as long as you wish for them to be frozen and nothing happens to them in the mean time.
With vitrification, which is the procedure used today, 98% of embryos survive thawing.
So it is a very effective procedure for embryo freezing and thawing.