In the 1949 article “Revival of Spermatozoa after Dehydration and Vitrification at Low Temperatures,” researchers Christopher Polge, Audrey Ursula Smith, and Alan Sterling Parkes demonstrated that glycerol prevents cells from dying while being frozen. Polge and his colleagues discussed several procedures in which they had treated sperm cells from various species with glycerol, froze those cells, and then observed the physiological effects that freezing had on the treated sperm. The researchers concluded that glycerol safely preserves sperm samples from a variety of species. Polge, Smith, and Parkes’s 1949 article detailed one of the first successful uses of a chemical medium to preserve viable cells in a frozen state, a process that eventually enabled the first vertebrate embryo to be successfully conceived using frozen sperm.

In 1952, researchers Christopher Polge and Lionel Edward Aston Rowson, who worked at the Animal Research Center in Cambridge, England, detailed several experiments on protocols for freezing bull semen for use in the artificial insemination of cows. Freezing sperm extends the life of a viable sperm sample and allows it to be used at later times, such as in artificial insemination. The researchers examined the effects of freezing conditions on bull sperm and how well they produce fertilized embryos once thawed. Polge and Rowson concluded that bull sperm can retain its fertility throughout the freezing process and that frozen bull sperm can yield pregnancy rates of up to seventy-nine percent. Polge and Rowson provided the first conclusive evidence that frozen mammalian sperm, once thawed, can produce viable pregnancies.

Twentieth-century researcher Ernest John Christopher Polge studied the reproductive processes of livestock and determined a method to successfully freeze, thaw, and utilize viable sperm cells to produce offspring in animals. In 1949, Polge identified glycerol as a cryoprotectant, or a medium that enables cells to freeze without damaging their cellular components or functions. Several years later, Polge used glycerol in a freezing process called vitrification, which enabled him to freeze poultry sperm, thaw that sperm, and use it to fertilize vertebrate embryos. He later adapted those methods to be applied to several other species including goats, cows, and pigs, which enabled farmers to fertilize livestock with sperm or embryos after long-term storage. Additionally, Polge's development of methods to freeze and store living samples has equipped reproductive health researchers and medical professionals with the abilities to mass collect and store human sperm.

In 1983, researchers Alan Trounson and Linda Mohr published the article “Human Pregnancy Following Cryopreservation, Thawing and Transfer of an Eight-Cell Embryo,” hereafter “Human Pregnancy,” in the journal Nature. In the article, the authors describe an experiment that led to one of the world’s first pregnancies through cryopreservation, or freezing, of an eight-cell human embryo. They discuss an experiment conducted at the Monash University and Queen Victoria Medical Center in Melbourne, Australia. Prior to the article’s publication, scientists had reported on embryonic cryopreservation experiments with animals only. At the end of the article, the authors mention that the pregnancy ended in a spontaneous miscarriage due to problems unrelated to cryopreservation twenty-four weeks after embryonic transfer. Despite the miscarriage, “Human Pregnancy” is one of the first articles to describe a successful human pregnancy after cryopreservation, and demonstrated that cryopreservation, as part of in vitro fertilization treatment, was a viable option for humans as well.