Freezing

Embryo Freezing
Some couples are fortunate enough to collect a large number of embryos from one egg collection. Any remaining viable embryos that are not transferred into the woman's uterus during the month of treatment may be frozen ("cryopreserved") in small tubes and kept in storage in the embryo laboratory for future use. This allows the patient to limit the number of embryos transferred "fresh" without sacrificing the chance that the unused embryos could lead to a pregnancy. The embryos may be kept in storage for several years. By transferring frozen-thawed embryos into the uterus, some patients have achieved 2-3 pregnancies in different years from just one egg collection.

Egg Freezing
Egg freezing, with subsequent thawing, fertilization and creation of a successful pregnancy is an advancement that has eluded reproductive endocrinologists for the first three decades of in vitro fertilization. The major stumbling block was ice crystal formation that damaged the frozen egg.

For some time, the doctors at Houston IVF and CCRM have been studying competing technologies designed to avoid this problem. A process called vitrification uses a cryoprotectant to make water in the egg harden without formation of ice crystals. This technique has now been demonstrated to yield better pregnancy rates than other techniques such as slow freezing.

Our clinical trials using vitrification have demonstrated satisfactory freezing and thawing of eggs resulting in live births. Success has been improved by recognizing that directly injecting a sperm into the thawed egg, a technique called intracytoplasmic sperm injection (ICSI), is required for good fertilization rates after thawing.

For a better understanding, watch the video below of egg freezing at Houston IVF.