In what cases is sperm cryopreservation necessary? For those who are unable to have their sperm retrieved at the same time on the day of the egg retrieval procedure, the male partner may choose to freeze the semen in advance. This way, the semen can be thawed on the day of egg retrieval for in vitro fertilization. There are also cases where the sperm can be frozen and preserved before the start of treatment because of the health of the male partner, such as in cases where radiotherapy is required and the medications that need to be taken can significantly impair the quality of the sperm. There are also patients with traumatic testicular damage and fertility needs who can have their sperm cryopreserved for later use. Can cryopreservation damage sperm? Cryopreservation of semen means that semen is mixed with freezing solution, pre-cooled with liquid nitrogen vapor and then preserved at ultra-low temperatures. During the freezing process, the ultra-low temperature will cause the sperm cell fluid to solidify rapidly, and the cryopreservation fluid will play a protective role in it. The freezing solution can prevent the cells from increasing in size after freezing and the ice crystals from destroying the cell walls, so that most of the cells can survive the “extreme cold test”. Thawing is usually done in a 37°C water bath with heat, during which some of the sperm will not be able to “wake up”. Can I still use the thawed sperm? Yes. After freezing and thawing, although some of the sperm in the semen will “die”, there are hundreds of millions of sperm per milliliter of semen in a healthy man, and the remaining sperm will be selected to complete the fertilization mission. After thawing, sperm with good viability are selected for subsequent in vitro fertilization or artificial insemination through gradient centrifugation, or upstream methods. The sperm bank’s sperm donor is also used by freezing and thawing in this way.