Egg freezing or egg cryopreservation is a procedure in which a woman's unfertilized eggs are extracted, then dried, frozen and stored for future implantation. The process extends the time a woman can conceive a child beyond the typical fertility period, which significantly lowers in the late 30s and 40s.
Because it prolongs a woman's fertility window, egg cryopreservation has become increasingly popular among woman who have chosen to wait either because of their relationship status, career plans or an unfortunate health event.
A woman’s fertility peaks at 27 years old, but as age 40 rolls around, the rate of pregnancy drops to less than 10 percent. Therefore, egg freezing is most successful when the eggs are harvested before the age of 35 and is not usually recommended after the age of 39, due to declining egg quality.
Each egg freezing cycle takes four to six weeks to complete. The medically assisted process involves:
- Self-administered hormone injections plus birth control pills are prescribed for two to four weeks to obliterate the body’s natural hormones.
- Hormone injections are then prescribed to stimulate the woman’s ovaries and ripen numerous eggs for harvesting.
- With ultrasound guidance, a special needle is used to vaginally extract eggs from the ovaries. An average of 10 to 20 eggs per cycle are collected, at least 10 of which should be stored for future use.
- Extracted eggs are individually withdrawn from the specimen.
- Each egg is prepared for freezing by dehydrating it and applying an antifreeze mixture. Note: Human eggs are the largest cells in a woman’s body and they contain a significant amount of water. All water must be removed before freezing the egg because ice crystals can eventually damage it.
- Each egg is frozen and stored in liquid nitrogen at -196 degrees Celsius. Some labs choose to slow freeze the eggs, while others use a flash freeze process or vitrification.
- When the patient is ready to use the frozen eggs, each one is thawed and injected into a single sperm. The injection process is called intracytoplasmic sperm injection (ICSI).
- Once developed, three to four embryos are implanted into the woman’s uterus using a special catheter.
Egg cryopreservation costs about $10,000. In addition, there is a yearly storage fee, which averages $500.
When a decision is made to thaw the eggs for use, an additional cost of about $5,000 is incurred to thaw, fertilize, and transfer the embryos into the woman’s uterus.
Overall, the cost of egg cryopreservation runs parallel to in vitro fertilization (IVF) costs.
Frozen eggs can be stored indefinitely. If a woman chooses not to use her cryopreserved eggs to attempt pregnancy, there are several other options:
- Donate them to be used by someone else
- Destroy them
- Donate the eggs for research purposes
The success of achieving pregnancy using cryopreserved eggs depends upon a few factors: harvesting, freezing, thawing, fertilization, and implantation. Here are the statistics of the success rates:
- Post-thaw egg survival rate: 60-90%
- Fertilization rate for women up to 38 years old: 70-80%
- Pregnancy success rate per embryo transfer up to 35-50%
About 150 babies in the U.S. and 150,000 babies worldwide have been born via egg cryopreservation. There is no documented increase in birth or chromosomal defects noted versus using fresh eggs.
The choice to freeze eggs is a personal one. A limited number of patients have undergone this promising procedure. Studies continue to evaluate this evolving process.