Cryopreservation of embryos occurs after an egg is fertilized but before it is implanted for use attempting a pregnancy at a later date.
What is embryo cryopreservation?
Cryopreservation is a technique developed to freeze and then thaw embryos for use in vitro fertilization (IVF). During standard infertility treatment, certain hormones are given to the female patient to provoke her ovaries to develop more eggs than normal. These eggs are then retrieved and fertilized with sperm in a laboratory. Normally, there are more fertilized eggs — also known as embryos — than can be implanted in the woman’s uterus. This is where embryo cryopreservation comes in.
The act of freezing embryos can have many purposes including:
- Multiple IVF transfers – this the most common reason for freezing because additional transfers are useful if the initial fertilized egg fails to implant properly. It would be quite costly and time consuming to embark on a full IVF cycle after every attempt.
- Future use – even if an egg implants properly and then develops into a baby, the mother can choose to keep extra embryos frozen for a prolonged period of time in case she wishes to attempt another pregnancy in the future
- Donation to other parents – since the embryo does not necessarily have to be implanted in the same person who provided the egg, some couples choose to give their fertilized egg to other chosen individuals or make a blind donation to a couple in need
- Donation to science – this can help researchers discover new breakthroughs for those experiencing infertility
- Not wasting embryos – some individuals may simply not wish to destroy quality embryos for moral or religious reasons
- Undergoing treatment – it is also possible to freeze a fertilized egg before beginning a cancer treatment such as radiation or chemotherapy that can reduce or eliminate the chances of future pregnancy
How does embryo cryopreservation work?
Embryos may be frozen up to six days after initial retrieval takes place. However, not all embryos are candidates for cryopreservation. Only high-quality embryos that are not irregular and do not divide slowly are candidates. For this reason, cryopreservation is not recommended for patients over 40.
Once selected for cryopreservation, embryos are placed in a cryoprotectant solution and frozen at a temperature of –320 degrees Fahrenheit, usually using liquid nitrogen. It is estimated that somewhere between 60% and 90% of embryos successfully survived the freezing and thawing process.
The pregnancy rate of using these embryos is indistinguishable from using normal fertilized eggs and have shown no signs of increased birth defects. Embryos can remain frozen for years and still be viable. There are currently more than 500,000 embryos in storage in the United States.
What are the risks of embryo cryopreservation?
This process does not come without its risks including negative reactions to fertility drugs, rare complications with the egg retrieval procedure and the emotional risks that come with no guarantee of success.
IVF itself can be a costly endeavor, and choosing embryo cryopreservation for an extended period of time can add to that cost. It is important to get advice from a fertility clinic with expert reproductive endocrinologists. The Centers for Disease Control and Prevention and the Society for Assisted Reproductive Technology provide information online about the pregnancy and live birth rates of all fertility clinics in the United States.
To learn more about hormone embryo cryopreservation and how it could help you, contact your neighborhood Texas Health Care Obstetrics & Gynecology clinic in DFW.