Cryopreservation and Sperm Preservation

Cryopreservation and Sperm Preservation

Cryopreservation refers to the freezing of human embryos. Therefore, additional embryos can be preserved. Frozen embryos tend to remain viable for approximately ten years. The embryos are frozen to sub-zero temperatures such as -196 degrees Celsius. Cryopreservation has proved extremely beneficial for couples undergoing ARTs. Cryopreservation has enabled the avoidance of both ovarian induction (OI) and egg retrieval, two stages that are often necessary for several ARTs. As a result, if a patient fails to get pregnant from their first ART, they are able to quickly attempt a second trial. The embryos can be transferred during a normal or artificial cycle, and the patient does not have to undergo ovarian stimulation.

In a patient that has a normal cycle, embryos are transferred 5-6 days after ovulation occurs. An ultrasound is used to confirm the fact that ovulation has taken place. In patients with irregular periods, medications are used to control the menstrual cycle, and develop the endometrial lining. After the endometrium is prepared, Progesterone is administered and the embryos are transferred after 5-6 days.

There are a few problems with Cryopreservation. First of all, in some cases the eggs do not always survive the freezing and thawing process. Some embryos are not even suitable for freezing. The average survival rates for frozen embryos are approximately 40-60%. Sometimes, the freezing process results in the development of solution effects, extracellular or intracellular ice formation, and dehydration. All of these are damaging to the embryos. Recently, vitrification has been introduced to help prevent problems that arise due to ice formation. In vitrification, cryoprotectants are used prior to cooling. This helps lower the freezing point, and increase viscosity of the liquid. As a result, instead of crystallization occurring the liquid becomes an amorphous ice.

A couple that is using Cryopreservation must inform the center about their future intentions regarding the frozen embryos. A separate charge is listed for Cryopreservation.

Sperm can also be frozen and preserved in a similar manner. This is again advantageous to couples, since it allows sperm to be available in case of emergency. For example, situations can arise where a normally fertile man produces a less than adequate sperm sample. In such unforeseen circumstances, sperm that has been frozen can be used. This can prove extremely beneficial if a physician is unable to contact the couple. In many cases the window of opportunity is extremely small, and timing is crucial. Eggs cannot survive a long time after egg retrieval without being fertilized, thus a time delay in insemination of the culture media can have drastic consequences.