What is Embryo freezing?
Embryo freezing is a process that involves freezing and storing unused embryos. These embryos consist of fertilized eggs created during IVF, including intracytoplasmic sperm injection (ICSI). Researchers use a technique called cryopreservation, starting the process with freezing.
The clinic stores the frozen embryos and can thaw them when needed for future IVF cycles. This helps patients save time and money. The woman will not need extra egg retrievals or as many medications in future cycles.
People usually choose to freeze their embryos to keep the option of becoming a parent later. Reasons for considering cryopreservation include cancer treatment, ageing, or the risk of injury from medical conditions or military deployment.
How are embryos frozen and stored?
Reproductive endocrinologists use two methods to freeze embryos: vitrification (flash freezing) and slow programmable freezing. While these methods differ, both involve cooling the embryos with cryoprotectants or "antifreeze" fluids. Since embryos mostly contain water, freezing can cause ice to form and damage the cells when someone thaws them. Cryoprotectants help prevent ice crystals from forming, protecting the embryos from harm during the freezing process.
In the slow-freezing method, embryologists place embryos in a machine that cools them gradually in stages. After adding cryoprotectants, the embryos are frozen and stored in liquid nitrogen at -321°F. This process takes about two hours.
Vitrification, a newer and more successful method, uses a solution with a higher concentration of cryoprotectants. Researchers quickly freeze the embryos in liquid nitrogen, turning them into a glass-like substance. This process prevents ice crystals from forming, improving the chances of the embryo's survival and viability after thawing. At Arockia Virgin Fernando Clinic, the staff exclusively uses vitrification for the cryopreservation of all new embryos.
No matter the method, frozen embryos remain paused in time. All biological activity, like cell growth and death, stops.
When needed, someone gently thaws the embryos and soaks them in fluids. This process removes the cryoprotectants and adds water back to the cells. People can store frozen embryos for a long time. Researchers stored the longest frozen embryo for 19 years, which led to a healthy pregnancy.
What are the risks of freezing embryos?
Research shows that freezing and thawing embryos does not harm babies born through IVF. Storing an embryo for a longer time does not impact the success rates of IVF.
With advancing technology, the difference in pregnancy rates between frozen and fresh embryos is now minimal. The stimulation process for frozen embryo transfer is gentler. Hormone levels are closer to normal, which may help improve pregnancy rates.
Ice crystals that form when freezing slowly can harm an embryo during thawing. This is one reason why vitrification is the preferred method for cryopreservation. Research shows that children born from frozen embryos do not have a higher risk of congenital disabilities. This is the same for those born from fresh embryos.
FAQ
Freezing embryos can be very worthwhile for many individuals and couples. It's particularly valuable if you're undergoing IVF and have extra high-quality embryos after transfer, want to preserve fertility before medical treatments like chemotherapy, wish to delay parenthood while preserving current fertility potential, or are planning multiple children without repeating the full IVF cycle. The cost typically ranges from ₹15,000-₹30,000 for initial freezing plus annual storage fees of ₹10,000-₹25,000, which many find reasonable considering it eliminates the need for repeated egg retrievals and can increase overall chances of having a baby.
The success rate of embryo freezing is excellent with modern vitrification techniques. Approximately 90-95% of frozen embryos survive the thawing process, which is significantly higher than older slow-freeze methods. Pregnancy rates with frozen embryo transfer (FET) range from 40-60% per transfer for good quality embryos, with success rates influenced by the woman's age at the time of freezing, embryo quality and stage at freezing, and the uterine environment during transfer.
Good candidates for embryo freezing include women undergoing IVF who have surplus embryos after fresh transfer, individuals facing cancer treatments or medical procedures that may affect fertility, women wanting to preserve fertility at their current age, couples using preimplantation genetic testing (PGT) who need time for results, women with conditions like endometriosis or PCOS planning future pregnancies, and those who need to delay transfer due to ovarian hyperstimulation syndrome (OHSS) or thin uterine lining.
Yes, babies born from frozen embryos are just as healthy as those from fresh embryos or natural conception. Extensive research spanning decades has shown no increased risk of birth defects, developmental delays, or genetic abnormalities. Some studies even suggest slightly lower rates of certain complications like preterm birth compared to fresh embryo transfers, possibly because the uterus has more time to recover after stimulation. Millions of healthy babies worldwide have been born from frozen embryos.
The embryo freezing process involves several steps. First, embryos are created through IVF by fertilizing eggs with sperm in the laboratory. The embryos are then cultured for 3-6 days until they reach either the cleavage stage (day 3) or blastocyst stage (day 5-6). High-quality embryos suitable for freezing are selected by embryologists. The chosen embryos undergo vitrification, a rapid freezing process using cryoprotectants to prevent ice crystal formation. Finally, the embryos are stored in liquid nitrogen at -196°C where they can remain viable indefinitely.
The actual freezing procedure takes only about 15-30 minutes per embryo. However, the entire process from egg retrieval to freezing spans 3-6 days, as embryos need time to develop in the laboratory before being frozen. Day 3 embryos can be frozen after 3 days of culture, while blastocyst-stage embryos (which generally have better survival and pregnancy rates) are frozen after 5-6 days of development. The vitrification process itself is very quick, taking just minutes to complete.
Most fertility specialists recommend resting for 15-30 minutes immediately after the embryo transfer procedure. You can typically resume normal daily activities the same day or the next day, though it's wise to avoid strenuous exercise, heavy lifting, and high-impact activities for 2-3 days. There's no medical evidence that prolonged bed rest improves success rates, and most doctors encourage normal, gentle activity. You should avoid sexual intercourse, hot baths, and swimming for about a week, and take it easy emotionally while waiting for the pregnancy test, which is usually done 9-14 days after transfer.
The best age to freeze embryos is in your late 20s to early 30s when egg quality and quantity are at their peak. Women under 35 generally have the highest success rates, with better embryo quality and higher chances of pregnancy later. However, freezing embryos can be beneficial at any age before menopause. Women in their late 30s and early 40s can still successfully freeze embryos, though they may need more IVF cycles to obtain good-quality embryos. The key advantage of freezing earlier is that you preserve your fertility at your current biological age, regardless of when you decide to use the embryos.
Frozen embryo transfers (FET) often have success rates comparable to or sometimes higher than fresh embryo transfers. Many studies show FET pregnancy rates of 40-60% compared to 30-50% for fresh transfers, though this varies by individual circumstances. The potential advantages of frozen transfers include allowing the uterus time to recover from hormonal stimulation, enabling optimal timing for uterine receptivity, permitting genetic testing of embryos before transfer, and reducing the risk of ovarian hyperstimulation syndrome. The ability to select the best-quality embryos and transfer them in a more natural cycle often contributes to the success of FET.
The embryo freezing process itself is not painful at all because it occurs in the laboratory with embryos that have already been created—you won't feel anything during the actual freezing. However, the IVF process leading up to freezing involves some discomfort: daily hormone injections for 10-14 days can cause mild pain and bloating, and the egg retrieval procedure may cause cramping and discomfort, though it's performed under sedation. The frozen embryo transfer later is generally painless, similar to a pap smear, requiring no anesthesia. Most discomfort is associated with the initial IVF cycle rather than the freezing or transfer procedures themselves.