Dr. Firuza Parikh
Egg Freezing - 11th April 2017
Today, IVF is a household word and is considered as a routine treatment rather than the revolutionary advance it was 38 years ago. However, several offshoots of the IVF procedure have benefits that patients enjoy and utilize. One such advance is Oocyte freezing.
At birth, a woman is born with half a million eggs. Unlike a man who continues to produce sperm throughout most of his life, a woman has a finite number of eggs which are by and large depleted in the early forties. These eggs are stored in her ovaries, each inside its own sac called a follicle. At puberty, her body begins producing various hormones that cause the eggs to mature. This is the beginning of her first cycle; it's a cycle that will repeat throughout her life until the end of menopause. At time of ovulation, the blood supply to the ovary improves and the ligaments contract, pulling the ovary nearer to the fallopian tube, allowing the egg, once released, to find its way into the tube. Just before ovulation, a woman's cervix secretes an abundance of clear "fertile mucous". Fertile mucous helps the sperm's travel toward the egg. Inside the fallopian tube, the egg is carried along by tiny, hair like projections, called "cilia" toward the uterus. Fertilization occurs if the time is opportune.
Egg quality and quantity both start declining slowly in most women in the mid-thirties. Both quantity and quality of eggs decline more rapidly after about the age of 37. It becomes much more difficult to get pregnant after 40 and by 43 years’ conception in women is more anecdotal than a reality. The increased rate of chromosomal abnormalities in eggs of women with advanced age is the main cause of this qualitative decline. Thus the woman's Biological Clock slows down by 37 and stops ticking by 42. Egg freezing can potentially lock in the quality of the woman's eggs at the age when she freezes them. She can then preserve her fertility by using those frozen eggs years later when the quality of the remaining eggs in her ovaries are significantly diminished. The quality of frozen eggs does not decline significantly over time.
What is the Right time for Egg Freezing?
The chances for pregnancy are greater if a woman uses "younger" eggs i.e. eggs she froze in her 20s or early 30s, rather than later. However, a woman can also freeze her eggs at 40, but the expected success rate is low. Thus the earlier a woman freezes her eggs, better the quality when those eggs are eventually thawed.
Who is a candidate for Egg freezing?
Egg freezing can be of immense help to any woman who wishes to preserve her fertility to a later date in the future:
Some of the common indications for egg freezing are
- In order to delay childbearing for personal and social reasons.
- In women diagnosed with cancer prior to starting chemotherapy.
- Risk of early menopause
- Objections to storing frozen embryos for religious, or moral reasons
- While a woman is waiting for the right partner.
- Couples who are undergoing in vitro fertilization (IVF) and are not able to fertilize eggs the same day due to non-availability of sperm from the male partner.
- Couples undergoing IVF who have surplus eggs and do not wish for those eggs to be fertilized and frozen as embryos.
Freezing eggs can be a very reassuring and empowering step, and it allows women to take control of their own fertility.
What is the Egg freezing process?
Although sperms and embryos are easier to freeze, the egg being the largest cell in human body contains a large amount of water which can prevent optimal freezing. When frozen, ice crystals form that can destroy the cell. The egg needs to be dehydrated and the water needs to be replaced with an anti- freeze substance prior to freezing in order to prevent ice crystal formation. Also the shell of the egg hardens when frozen, hence sperm must be injected with a needle to fertilize the egg using a standard technique known as ICSI(Intra-cytoplasmic sperm injection)
The Anti-Mullerian Hormone (AMH) is a hormone in the ovarian follicles. It is a key in gauging a woman's fertility. The importance of AMH as regards to egg freezing cannot be over emphasized. AMH levels can help determine the number of eggs you may be able to retrieve as its levels correlate with the number of ovarian follicles, making the hormone a good indicator of ovarian reserve. Testing these levels is also helpful in determining whether a woman has diminished ovarian reserve or premature ovarian failure or PCOS. Since the levels of AMH in the blood do not fluctuate much, the test can be done at any point during the menstrual cycle. Women with higher concentrations of AMH have a superior response to ovarian stimulation and are likely to produce more eggs for freezing as compared to women with low AMH.
A low AMH indicates there is a problem with the quantity and quality of a woman's eggs. Women with low AMH tend to have poor response to fertility drugs used for ovarian stimulation. Hence the anti-Müllerian hormone (AMH) testing is the best and most accurate predictor of a woman’s remaining ovarian reserve.
The procedure of Egg Freezing
The procedure of egg freezing has multiple steps. Ovulation Induction is the first step in the process.
- Ovarian Stimulation:
At the beginning of the menstrual cycle, synthetic hormones are administered in order to stimulate multiple eggs. Several different be needed, including
- Medications for ovarian stimulation.
To stimulate your ovaries, typically medication such as FSH or human menopausal gonadotropins are employed along with a GnRH antagonist to prevent premature ovulation. During treatment, there are follow-up visits sonography scans in order to monitor the development of egg containing mature follicles. Blood tests are conducted on a regular basis to see the response to ovarian-stimulation. Estrogen levels typically increase as follicles develop and progesterone levels remain low until after ovulation. When the follicles are ready for egg retrieval — generally after eight to 14 days of injections the trigger of human chorionic gonadotropin or decapeptyl is given to bring about the final maturity of the oocytes.
- Egg retrieval
Egg retrieval is done by transvaginal ultrasound under mild anesthesia. A suction device connected to the needle gently aspirated the egg from the follicle. Multiple eggs can be removed from the follicles in about 15 to 20 minutes
Shortly after the eggs are harvested, they're cooled to subzero Celsius temperatures to stop all biological activity and preserve them for future use. The makeup of an unfertilized egg makes it more difficult to freeze and lead to a successful pregnancy than does the makeup of a fertilized egg (embryo). Embryo labs use substances called cryoprotectants to help prevent ice crystals from forming during the freezing process. The most commonly employed freezing process is Vitrification. In this method, high initial concentrations of cryoprotectants are used in combination with cooling so rapid that intracellular ice crystals don't have time to form. The eggs are frozen the same day and stored in liquid nitrogen tanks. The entire process takes approximately 4-6 weeks to complete the egg freezing cycle and is consistent with the initial stages of the IVF process.
Ideal number of eggs expected to be frozen
During an egg freezing cycle, an attempt is made to extract multiple eggs in the same sitting. Fertility medications in this “super ovulation” cycle help in achieving a greater yield. Since not every egg will result in a pregnancy, a large number of eggs are extracted at once to give the best chance of harvesting viable eggs, and to have a high enough cache for subsequent pregnancy attempts later. Multiple egg retrieval cycles may be needed to achieve the goal for optimal number of eggs. Women over 30 should ideally have at least 20 eggs cryopreserved.
Long term safety
There have also been over 5000 children born worldwide from frozen embryos using primarily slow-freeze cryopreservation techniques, without an increase in birth defects. The largest published study of over 900 babies from frozen eggs showed no increased rate of birth defects when compared to the general population. Additionally, results from one study showed no increased rates of chromosomal defects between embryos derived from frozen eggs compared to embryos derived from fresh eggs. In 2014 a new study showed that pregnancy complications were not increased after egg freezing. Although these data are reassuring, it will take many years of follow-up to ensure that babies born from egg freezing technology do not have higher rates of birth defects than those conceived otherwise. The American Society of Reproductive medicine (ASRM) does not consider egg freezing as an experimental procedure anymore.