In Depth: Fertility Preservation: Freezing Eggs vs. Embryos for the Future
Damien Fertility Partners is at the forefront of freezing (cryopreserving) eggs and embryos. We utilize the most advanced cryopreservation technique, vitrification, an ultra-rapid technique that instantaneously brings the cells to -196 degrees centigrade. A solution (cryoprotectant) that decreases the water in the cells enables this technique to preserve cells and embryos for hundreds of years.
However, which choice is best for the patient or couple who wants to plan for the future? Freeze the eggs or the embryos? Either one has advantages. Both options maintain the ability to conceive in the future. Egg freezing preserves the woman’s ability to choose a future Partner. Freezing embryos allows for better evaluation of the quality of the cells frozen and an improved prediction of future success in implantation and pregnancy. (IVF). Modern techniques utilize injectable fertility medicines (FSH, Follicle Stimulating Hormone) to increase the number of mature eggs or oocytes produced in ovulation. These small needle injections are self-administered for 8 – 11 days, followed by another injection of hCG or leuprolide to complete egg maturation and ovulation. Egg retrieval with an ultrasound-guided needle is a quick surgical procedure requiring light anesthesia. The eggs are then transferred to the IVF laboratory.
With egg freezing, there are no sperm and no fertilization. Embryos are not created. We only freeze the mature eggs, which are ready for fertilization when thawed in the future. Very little quality evaluation is possible when freezing eggs. The prediction of future success when thawed is affected by the woman’s age at the time they are frozen, and a superficial visual assessment of the egg and its surrounding protective cells called the cumulus. This option is best for the single woman with no committed partner who wishes to preserve that future option. However, it usually requires more eggs be frozen in older women to preserve future fertility. A percentage calculation of future success is possible but subject to significant variation.
Once a woman or couple chooses to create embryos and freeze them for future conception, there are no options for a different partner for these embryos. Consequently, it is not a good option for a single woman with no committed partner. The ability to predict future success and even the health of the child now becomes possible. For this technique, the egg is fertilized with the partner’s sperm. Donated sperm can also be utilized by same-sex female couples or by women who are committed to having a child as a single woman. The resulting embryos can then be “grown” in the IVF laboratory for 5-6 days until they reach the blastocyst stage of development. Achieving this stage ensures a higher level of future success beyond that expected from an egg.
Also, the blastocysts may then have a few peripheral cells removed. DNA is then separated and sent to a lab that can “read” the DNA and predict the status of the chromosomes. This technique, known as PGT-A, preimplantation genetic testing for aneuploidy (abnormal chromosomes), allows us to determine if the embryo is normal. By using this technique, we can predict a more accurate percentage of future success when thawed. A single normal embryo offers a nearly 75% chance of success with a healthy child.
Freezing oocytes provides greater flexibility for a woman to decide on a future partner. Still, freezing embryos provides a more secure prediction of future success. Many details can be discussed with a patient or couple to enhance understanding of these choices. Our physicians and nurse practitioners look forward to the opportunity to further review these fertility options with you.