Introduction
A female reproductive life span is finite and depends on the number of eggs or oocytes with which she is born. Some women cannot get pregnant at the most fertile stage of their lives for various reasons, such as cancer, a medical condition affecting their fertility, or they wish to get pregnant later in life. Egg freezing, also known as oocyte cryopreservation, is a blessing for such women. Egg freezing is a great development in the field of assisted reproductive technology(ART). The first birth from a frozen oocyte successfully happened in 1986. This technology has offered acceptable pregnancy outcomes since then. However, it does have some challenges and risks. This article discusses egg freezing and related issues in detail.
What Is Egg Freezing?
Egg freezing or oocyte is a method of preserving women’s ability to get pregnant in the future. A woman is born with a certain number of eggs, and no more eggs are produced after birth. The chances of getting pregnant naturally decrease as she gets older because the number and quality of eggs drop. Egg freezing can be done to preserve fertility when the woman is young, and the quality of eggs is the highest. It involves extracting a woman’s eggs and freezing and storing them to preserve her reproductive potential. It is a boon for women who wish to delay pregnancy due to personal, medical, professional, financial, or psychological reasons but preserve their fertility in case of anticipated decline. It is generally an option for women under 38 years who wish to have genetically related children at a future date. Most women who opt for egg freezing attempt it in their early 30s.
Egg freezing is different from embryo freezing or embryo cryopreservation. Embryo freezing involves freezing the fertilized egg called embryo (an egg is fertilized by a sperm and forms an embryo). Whereas egg freezing does not require sperm to fertilize eggs, and unfertilized, mature eggs are frozen and stored.
Who Needs Egg Freezing?
Egg freezing is an option for those women who are not ready to get pregnant now but want to conceive in the future and become genetic parents. Women can consider egg freezing for various reasons, such as:
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Surgery that can cause damage to the ovaries.
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Cancer treatment, such as pelvic radiation therapy or chemotherapy, can affect fertility.
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Ovarian disease with risk of ovary damage.
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Chromosomal abnormalities or a family history of early menopause cause a risk of premature ovarian failure.
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Genetic mutations may require the removal of ovaries.
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Fertility preservation for personal or social reasons to delay pregnancy.
How to Prepare for Egg Freezing?
Those women who are considering egg freezing should look for a fertility clinic with a high success rate and expertise in the field. Professionals specializing in this field are called reproductive endocrinologists. Before starting the egg-freezing process, a woman is likely to undergo tests such as ovarian reserve testing, blood test, ultrasound, and infectious disease screening. Ovarian reserve testing to check for the quality and quantity of eggs by testing the concentration of estradiol and follicle-stimulating hormone in the blood on the third of the menstrual cycle. A pelvic ultrasound and blood tests will be done to get complete detail of ovarian function. These tests decide whether the women can go for egg freezing or not. Infectious disease screening is done to screen for diseases such as hepatitis B, C, and HIV (human immunodeficiency virus) and prevent the affected egg sample from contaminating the other samples by storing them separately.
How Are Human Eggs Retrieved and Frozen?
The complete process of egg freezing involves three different stages - ovarian stimulation, egg retrieval, and freezing.
1. Ovarian Stimulation- The woman is given certain medications, which are synthetic hormones to stimulate the ovaries to boost egg production and help the eggs mature. Typically one egg is released by an ovary monthly. Medications are given in injectable form for ovarian stimulation and to prevent premature ovulation. The doctor will monitor the body’s response to these medications during this phase through blood tests. Follow-up visits include vaginal ultrasounds to determine the development of ovarian follicles (the sacs where the eggs mature). After 10 to 14 days, when the follicles are ready for egg retrieval, another medication is injected to help the eggs mature.
2. Egg Retrieval- This procedure is done under sedation or general anesthesia. The common approach adopted for this procedure is transvaginal ultrasound aspiration, which involves inserting an ultrasound probe through the vagina to identify the follicles. Then a needle is guided through the vagina into the follicle. Using a suction device connected to the needle, the eggs are removed from the follicle. Up to 15 eggs per cycle can be retrieved, although it is not always possible for women with low ovarian reserve or low egg count. Studies suggest that the more eggs retrieved, the better the chances of birth. After the egg retrieval, the woman may feel cramps, feeling of pressure, or fullness, which might continue for weeks as the ovaries remain enlarged.
3. Freezing- Immediately after the unfertilized eggs are retrieved, they are cooled at subzero temperatures for preservation and future use. Vitrification is a term commonly used for egg freezing. High concentrations of substances called cryoprotectants that prevent the formation of ice crystals during the freezing process are used for rapid cooling. Unfertilized eggs are a bit more difficult to freeze and lead to a successful pregnancy than a fertilized egg (embryo).
4. After the Procedure- Women can resume their normal activities after a week of egg retrieval. They should avoid unprotected sex to prevent unintentional pregnancy. The doctor should be contacted immediately if one experiences high body temperature (fever), severe abdominal pain, difficulty urinating, heavy vaginal bleeding, or weight gain of more than two pounds in 24 hours.
How Are Frozen Human Eggs Used in the Future?
When the woman is ready to get pregnant and use the frozen eggs, these cryopreserved eggs are assessed after placing them in the warming solution. The eggs that survive the freezing process are fertilized with intracytoplasmic sperm injection (ICSI), which involves injecting a single sperm directly into the egg. The fertilized eggs will then grow in the culture until the embryo is ready to transfer into the uterus. This is called in vitro fertilization (IVF) method to achieve pregnancy.
How Successful Is Egg Freezing?
The process of egg freezing has evolved over decades and has shown some promising results. Egg freezing is a relatively new technique and does have much data on success rate, but clinical pregnancy rates are approximately estimated between four to 12 percent per egg. However, its success rate depends on various factors that include the age of women at the time of egg freezing, the method of cryopreservation or freezing, and the total number of eggs frozen. Age while egg freezing is the most critical factor. There is no clear-cut recommendation, but freezing done at a younger age maximizes the quality and quantity of eggs that can give better results and high success rates. Egg freezing at the advanced stage requires multiple egg retrieval cycles and hence increasing the mental, physical and financial burden on the women undergoing the process. Studies have shown that egg freezing is less beneficial at ages 25 to 30 years as women of this age group are less likely to utilize the frozen eggs in the future, and it provides maximum benefits to women of ages 32 to 37 years.
What Are the Risks of Pregnancy at an Advanced Age?
There are medical risks for the women and their future children associated with pregnancy at an advanced age, which is expected delivery after 35 years of age. IVF is generally a safe procedure, although some women might experience side effects. The major risk of the procedure is that it might not work and give the expected results. All the risks should be communicated to women who opt for egg freezing. The medical risk to women and their offspring include:
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Risk to Women- The risks related to egg retrieval procedure include infection, bleeding, and a small risk of ovarian hyperstimulation syndrome (due to excessive response to hormones, the ovaries swell and leak fluid in the body). Women at an advanced age are at high risk of developing gestational diabetes, cesarean delivery, preeclampsia (a serious pregnancy complication characterized by high blood pressure), and preterm delivery of a baby with low birth weight. These risks differ widely depending on the health status of women and maternal age at the time of delivery.
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Risk to Offspring- Along with premature birth and low birth weight, there are incidences of risk of congenital structural abnormalities with IVF. There is also evidence of an increased risk of structural cardiac anomalies and cancer for these children. More research is required to determine the risks to children born from frozen eggs and IVF births.
Conclusion
Egg freezing has evolved over the past three decades into a well-established technology with impressive outcomes. It is inaccessible to women who are not financially secure and is a privilege for financially sound women. Egg freezing reinforces the value of having genetically related offspring, which may not be of equal importance for all women. The competing perspectives and all information available should be provided by the healthcare professional to women choosing egg freezing.
