The most basic reproductive biology includes the meeting of a sperm and an egg, or oocyte, to make an embryo. What many don’t realize is that while people can continue to produce new sperm long into older age, an individual is born with all the eggs they will ever have, roughly 2-7million, and this number steadily declines over time. In fact, at puberty a person has only 300,000 eggs remaining. Thereafter, every month (whether on birth control or not) several eggs compete to be the lucky one that gets to ovulate in hopes of meeting that special sperm, and all of the competing eggs that didn’t ovulate are lost, further reducing the number of available eggs for future fertilization. As we age, there are less and less eggs competing each month, and of those available to compete, there are fewer genetically normal eggs. In short, with age, both the quality and quantity of eggs diminish.
Oocyte cryopreservation, commonly referred to as “egg freezing”, is the process by which eggs are harvested and frozen for later use. Once harvested eggs are frozen, they are presumably good indefinitely, suspended in time until the individual chooses to thaw them in order to start a family. Statistically, the quality and quantity of eggs starts to diminish at a faster rate around age 35 when a person is medically considered to be “advanced maternal age”. This is not a steadfast rule, however. Some people will have egg decline earlier and some will experience it later, but all people will experience it eventually. Changes in the menstrual cycle are often a later sign of this decline in ovarian reserve.
Because the quality and quantity of eggs starts to decrease as an individual approaches age 35, freezing eggs at a younger age is ideal. However, freezing eggs at a very young age for the sole purpose of electively delaying childbearing may prove to be a waste of time and money, since an individual may get pregnant the old fashioned way without ever using their frozen eggs. For people who have invested in long educational and career goals and haven’t chosen to have a child before the age of 35, freezing younger, healthy eggs provides a way to potentially prolong their reproductive years. Many other people may find egg freezing a desirable way to preserve their fertility, including those faced with cancer or other diseases that requires treatment that may impair fertility, as well as single and divorced people who don’t want to raise children alone and have yet to find the elusive Mr. (or Ms.) Right.
The process of egg freezing is identical to that for IVF, or in vitro fertilization, just without the fertilization part. After meeting with a doctor who specializes in Reproductive Endocrinology and Infertility (REI), a time will be determined according to one's personal schedule and menstrual calendar to start the process. It may be necessary to start birth control or hormone shots for a few weeks in preparation to synchronize one's ovaries and eggs. Afterwards, the process of stimulating the ovaries with hormonal injections to keep all the eggs growing that would normally be in competition that month for ovulation. No more eggs can be stimulated than would otherwise be competing in any given month – that number is already set by an individual's body. There is no way to recruit more eggs to stimulate beyond what the body body naturally offers that cycle.
Once the schedule is set, stimulation with 2-3 hormonal injections per day to encourage growth and maturation of the eggs begins. These injections last for roughly 10 days. During this time visits to the doctor will occur every 1-3 days for blood work and vaginal ultrasounds. A vaginal ultrasound is the best way to track the growth of the follicles, which are fluid-filled cysts that each contain an egg. Once the doctor determines it is time to harvest the eggs from the follicles, an injection is needed to “trigger” ovulation of these eggs. The process culminates with a minor outpatient surgical procedure for “harvesting” the eggs that often takes less than 30 minutes--this is the egg retrieval. It is usually performed under a very light anesthetic. The person is completely asleep and cannot feel or remember anything, but is breathing on their own. The follicles are visualized with a vaginal ultrasound and are pierced using a long needle, leaving no visible incision. The needle is connected to suction, which drains the follicles of all the fluid and cells, including the single egg inside. After the egg retrieval is finished, the doctor will assess how many eggs were retrieved, and their maturity is assessed the very next day; only mature eggs will be frozen. Complications are very rare and most people are able to return to work the day after egg retrieval.
Once the decision is made to utilize these frozen eggs, it is important to keep in mind that not every thawed egg will result in pregnancy. Just as with fresh eggs, not every mature egg that was frozen will fertilize after it is thawed. Of those that do fertilize after thawing, not every embryo will grow, and not every growing embryo will implant and result in a healthy baby. The good thing is that technology has greatly improved the rate of survival of frozen eggs when thawed. Historically, many providers advocated embryo freezing over egg freezing for people wishing to preserve their fertility. However, with the currently improved thawed egg survival rates, people who freeze eggs can expect similar pregnancy rates to those using fresh eggs.
If you have questions regarding fertility preservation, don’t hesitate to speak with an REI specialist to help determine if you are a good candidate for egg freezing.
Dr. Sara J. Mucowski finished a 6-year combined Bachelor of Science/Medical Degree (BS/MD) program with Villanova University and Drexel University College of Medicine. After graduating with honors, Dr. Mucowski went to Galveston, Texas, where she completed her residency in Obstetrics and Gynecology at the University of Texas Medical Branch (UTMB). She then went on to complete a fellowship in Reproductive Endocrinology and Infertility at the University of Southern California (USC) in Los Angeles, CA. . She recognizes that every situation is unique, and requires treatment to be tailored individually to maximize success.
You can follow Sara on Instagram @saramucowskimd!
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