Cryopreservation of semen involves the cooling of a sperm and storage at a temperature where all metabolic processes are arrested. In practice, frozen sperms are stored at temperature of -196°C in liquid nitrogen.
Men can go for either “long Term" freezing or “short term" freezing.
Indication for “Long term" freezing:
Man undergoing chemo or radiotherapy which might lead him to sterility.
Indication for “short term" freezing:
Men who can not produce semen sample on demand at the time of IUI or IVF.
Man who cannot be present at IUI or IVF time.
Person who has variation in sperm count.
Once semen is collected, it is analysed for volume, viscosity, pH, total count, morphology, motility, sluggish etc.
Once analysis is over cryoprotectant is added into the semen which will prevent damage caused by freezing.
Specimen is then divided into aliqouts and subjected to freeze either by mechanical freezing method or by controlled rate freezing.
At -196°C in liquid nitrogen all the metabolic activity is halted, and semen can be preserved for many years.
With the increasing spread of AIDS and other sexually transmitted diseases (STD) in India and other countries, the importance of using properly tested and quarantined semen, for the treatment of infertility, has gained great importance. In most developed countries, the use of fresh untested semen for donor insemination has been discontinued to prevent the spread of these diseases through insemination procedures. These samples are screened and quarantined to ensure safe donor insemination. Stringent criteria are used to select donors and semen samples are processed and preserved under optimized conditions. All the records of semen samples and donors are meticulously maintained under strict confidentiality.
Oocyte [egg] freezing is a relatively new technique allowing oocyte to be stored for a long time at temperature below freezing point. To achieve this, the oocyte is placed in a freezing solution and then cooled very slowly using a computer assisted freezing machine.
Oocytes [eggs] can be stored below –196°C and can be reused whenever required at a later date. As long as the temperature is maintained, there is no time limit of storage. Efficient technique of freezing and thawing was developed in the year 1986, but the first successful report of normal development of cyropreserved human oocytes to the hatching blastocyst stage was in year 1995 by Gook et al.
Woman undergoing chemotherapy or radiotherapy for the treatment of cancer can freeze their oocyte before therapy, as cancer treatment might harm their ovaries & so damage their future fertility.
Woman who is suffering from certain medical conditions where the result is likely to be premature ovarian failure. In such case woman can go for oocyte freezing.
Woman less than 35 years who wish to preserve the eggs for future use.
Because oocyte freezing is a relatively a new technique it is difficult to predict the success of the process. More than 100 babies have been born around the globe with this method. There is not enough statistics for the success of program.
Studies on mice as well as human oocytes suggest that there is no damage of intricate structures with in the egg, or structures responsible for organizing the chromosomes [the genetic building blocks with in the egg].There have been healthy babies born from this technique, but the safety of oocyte freezing is still to be proven.
Embryo freezing is a well established method of ART. The first frozen embryo baby was born in 1984. Embryos are frozen at any stage [Pronucleate, early cleared & blastocyst]. Embryos are mixed with a cryoprotectant fluid, which will protect embryos from damage during freezing process. Then this mixture is stored in liquid nitrogen using a specialized programmable machine.
Embryos are labelled and cryopreserved in cryo storage specially designed for maintaining the temperature at -196°C, in liquid nitrogen.
As long as it is kept at liquid nitrogen temperatures, the embryos will remain viable, with only theoretical loss being due to damage caused by ice crystallization. Different countries have different regulations concerning the length of time that embryos can be frozen.
Advantages of embryo cryopreservation are as follows:
Allows maximizing the potential for conception for IVF & prevents wastage of viable normal spare embryos.
For high risk woman of OHSS [Ovarian Hyper Stimulation Syndrome], embryos can be frozen and transferred into subsequent cycle.
Women with endometrial polyps, poor endometrium development, bleeding at the time of embryo transfer, embryo cryopreservation can be done and embryo transfer can be done in subsequent cycle.
For women who have difficulty for fresh embryo transfer because of cervical stenosis [inability to pass through cervical canal because the cervix is narrowed or scarred], embryos can be frozen.
Before cancer chemotherapy or radiotherapy, lady can freeze her embryos.
In a good freezing program, a survival rate of 75-80% should be expected. This loss is because of the freezing and thawing process.
Frozen /thawed embryos are transferred into the uterus in a natural cycle, a hormone replacement cycle or a stimulated cycle. All three methods have similar success rates.
It is an ultra rapid embryo freezing method. Vitrification is a process of converting something into a glass like solid, free of any crystal formation. Like for blastocyst, by adding cryoprotectant, water can be cooled until it hardens like glass without any ice crystals forming.