Step-by-Step process of embryo freezing in an IVF cycle

1. Egg retrieval (Ovum Pick-Up)

Around 36 hours after the trigger shot, eggs are retrieved through a minor surgical procedure.
The process is conducted under mild sedation or anesthesia to ensure patient comfort.
A thin needle is inserted into the ovarian follicles to aspirate (suction out) the eggs.

2. Fertilization in the laboratory

Retrieved eggs are combined with sperm to facilitate fertilization.
There are two main methods:
- Conventional IVF: The egg and sperm are placed together in a petri dish for natural fertilization.
- Intracytoplasmic Sperm Injection (ICSI): A single healthy sperm is injected directly into the egg, typically used for male infertility cases.
Fertilization success is assessed after 16-18 hours.

3. Embryo culture and Selection

Fertilized embryos are cultured in a specialized incubator for 3 to 5 days.
Embryologists monitor cell division and growth to identify high-quality embryos.
The embryos reach the blastocyst stage (Day 5 or 6), which has a higher implantation success rate.
Only the best-quality embryos are selected for freezing to maximize the chances of pregnancy.

4. Embryo freezing using vitrification

The selected embryos undergo a rapid freezing process called vitrification, which prevents the formation of damaging ice crystals.
Steps involved in vitrification:
- Embryos are treated with cryoprotectants, substances that protect them from ice formation.
- The embryos are then rapidly cooled to -196°C using liquid nitrogen.
- They are stored in specialized cryogenic storage containers.

5. Long-Term storage in cryo-tanks

The frozen embryos are carefully stored in liquid nitrogen tanks at sub-zero temperatures.
Embryos can remain frozen for several years without losing their viability.
Patients can choose to use them for future IVF cycles or donate them for research.

6. Thawing and Embryo transfer

When a patient is ready to conceive, the frozen embryos are thawed for transfer.
The thawing process involves carefully warming the embryos and removing the cryoprotectants.
Embryologists assess the viability of the embryos before transferring them into the uterus.
The embryo transfer is a simple, painless procedure, and pregnancy is confirmed through a beta hCG test after 10-14 days.

Success rates of embryo freezing

The success rate of frozen embryo transfers (FET) is comparable to or even higher than fresh embryo transfers.
Vitrified embryos have a survival rate of 95-98%, ensuring excellent pregnancy outcomes.
The chance of pregnancy depends on factors like embryo quality, uterine receptivity, and overall patient health.

Who can benefit from embryo freezing?

Couples undergoing IVF: Those who produce multiple viable embryos can freeze excess embryos for future attempts.
Women delaying pregnancy: Individuals who wish to postpone childbirth due to career, personal, or medical reasons.
Patients with recurrent IVF failures: Freezing allows multiple embryo transfers without repeating ovarian stimulation.
Cancer patients: Women diagnosed with cancer can preserve embryos before undergoing chemotherapy or radiation.

Risks and Considerations

While embryo freezing is a safe and widely used technique, there are some factors to consider:

Not all embryos survive the freezing and thawing process.
The success of future pregnancies depends on the quality of the embryos.
Some women may require additional uterine preparation before undergoing frozen embryo transfer.

Conclusion

Embryo freezing is a game-changer in reproductive medicine, offering flexibility, cost savings, and improved success rates for IVF patients. By preserving high-quality embryos, individuals can enhance their chances of pregnancy while reducing the physical, emotional, and financial burden of undergoing multiple IVF cycles. This advanced technique provides hope for those planning future pregnancies, facing medical treatments that may impact fertility, or seeking to optimize their IVF outcomes. Contact Bavishi Fertility Institute today to explore your options and take the next step toward a successful pregnancy.

Author bio

Dr. Parth Bavishi

Dr. Parth Bavishi, MD in Obstetrics and Gynecology, brings over 12 years of invaluable work experience to his role as Director of Bavishi Fertility Institute, leading a group of IVF clinics committed to helping couples realise their dreams of parenthood.

Bavishi Fertility Institute is dedicated to providing customised and personalised treatments which are simple, safe , smart and successful. Bavishi Fertility Institute works with success and satisfaction for all at heart. Providing an ideal blend of professional treatment and personalised care.

Dr Parth had special training in infertility at Bavishi fertility Institute, the Diamond Institute, USA, and the HART Institute, Japan.

Dr. Bavishi is a distinguished expert in his field. In addition to his clinical practice, Dr. Bavishi is the author of the acclaimed book, ‘Your Miracle in Making: A Couple’s Guide to Pregnancy,’ offering invaluable insights to couples navigating the complexities of fertility. He loves to empower patients to make the correct choice by education both online and offline.

His exceptional contributions have earned him the prestigious Rose of Paracelsus award from the European Medical Association. Dr Parth has been an invited faculty at many national and international conferences.

Beyond his professional endeavors, Dr. Bavishi is an avid traveller who finds solace in exploring new destinations. He also enjoys engaging his mind with brainy puzzles, always seeking new challenges and solutions outside of the medical realm.

FAQs

At what stage are embryos usually frozen—Day 3 or Day 5?

Embryos can be frozen at different stages of development, at Day 3 or Day 5. If embryos are good in quality and quantity but most fertility clinics prefer to freeze them at the blastocyst stage (Day 5 or 6). Freezing embryos at the cleavage stage (Day 3) is also equally effective. So, When to freeze , depends on embryo details just like a fresh cycle.

Does embryo freezing affect the genetic health of the baby?

No, research has shown that babies born from frozen embryos have the same genetic health and developmental outcomes as those conceived through fresh embryo transfers. The vitrification process used for freezing prevents damage to the embryo, ensuring a high survival rate upon thawing.

How long can embryos remain frozen?

Embryos can remain frozen indefinitely as long as they are stored in proper cryogenic conditions. Studies have reported successful pregnancies using embryos that were frozen for over 20 years. However, the decision to keep embryos frozen for a long time depends on personal, medical, and legal factors. In India special permissions is required for freezing longer than 10 years.

What happens if I decide not to use my frozen embryos?

If you choose not to use your frozen embryos, you have several options:

Research donation: Allow them to be used for scientific research.
Discarding: You can request the clinic to dispose of the embryos following ethical guidelines.

Can I transfer my frozen embryos to another fertility clinic?

Yes, frozen embryos can be transported to another fertility clinic if you decide to switch providers or move to a different location. The process involves specialized handling and transportation under cryogenic conditions to maintain embryo viability. Always check the legal and medical requirements before transferring.

Do frozen embryos have a higher chance of twins or multiples?

Frozen embryo transfers do not inherently increase the chances of twins, but the number of embryos transferred plays a key role. If multiple embryos are transferred, the likelihood of twins or triplets increases. Single embryo transfer (SET) is often recommended to reduce the risk of multiple pregnancies.

Is there a difference in pregnancy rates between fresh and frozen embryo transfers?

Frozen embryo transfers (FET) have pregnancy rates equal to or even higher than fresh transfers. This is because FET cycles allow the uterine lining to be better prepared, improving implantation success.

However in certain conditions fresh embryo transfers have better results. Fresh embryo transfers have less incidence of sone pregnancy complications. It is crucial to customize embryo transfer according to your medical condition.