Egg freezing involves three primary steps: induction of ovulation, retrieval of the eggs and freezing them.
- Ovulation induction
- Egg retrieval
Your doctor first stimulates the ovaries by injecting synthetic hormones such as follicle stimulating hormone or human menopausal gonadotropins to boost the production of multiple eggs. Follow-up visits will be scheduled to monitor the growth of the development of the follicles (from which eggs develop) until egg release. Blood tests may be ordered simultaneously to test the levels of various hormones that take part in this process. After about 8 to 14 days, your eggs will be ready for retrieval.
Transvaginal ultrasound aspiration, a minor surgical procedure is performed under sedation to remove the eggs from the ovaries. A needle is guided through the vagina with an ultrasound probe and the eggs are removed with the help of a suction device attached to the needle. Multiple eggs are removed from your ovaries.
Soon after collection, the unfertilized eggs are frozen at sub-zero temperatures with cryoprotectants, substances that prevent the formation of crystals during freezing. There are two methods of freezing. With the slow-freeze method, low levels of cryoprotectants are used and the eggs are frozen gradually. Following this, higher concentration of cryoprotectants are added. This helps protect the eggs from the toxins present in the cryoprotectants. The other method is called vitrification, and involves the use of high concentrations of cryoprotectants and cooling so rapidly that crystals don’t have the time to form. By either method, eggs can be stored for a period of up to 10 years.
When the eggs are required, the frozen eggs are thawed, and allowed to fertilize with sperm in the lab or sperm is directly injected into the egg via intra-cytoplasmic sperm injection (ICSI) procedure, and implanted via in vitro fertilization (IVF) in the womb.