Embryo cryopreservation can be an essential part of the in vitro fertilization (IVF) fertility treatment process, especially in some cases like PCOS. Fertilized dividing embryos can be preserved for many years with special cryo protectants using Vitrification technology and are amenable for future use. Cryopreservation can increase the likelihood of achieving pregnancy for patients as provides multiple attempts of transfer cycle and enhances cumulative success. At times, clinicians themselves might consider freezing the embryos in a particular IVF cycle and defer the transfer to subsequent cycle because of some hormonal derangements or endometrial advancement . This synchrony then ensures better embryo- endometrium dialogue and better implantation success. Cryopreservation also allows couples to continue to see their families grow as IVF cycles can be repeated, years later, from the same group of eggs originally recovered for treatment.
Embryo freezing (cryopreservation) is a method of preserving the vitality of embryos obtained from IVF treatment by carefully cooling them to very low temperatures using an ultra rapid freezing process called Vitrification which is nearly 600 times faster than the traditional slow freezing, resulting in better embryo survival and quality after thawing. Vitrification (freezing) is the latest technique for freezing embryos in IVF procedures and incubates in a special substance cryoprotectant, which replaces water in their cells. This will protect the embryos from damage caused by ice crystals forming. During the freezing process, the embryos are rapidly frozen and kept at very low temperatures (-196oC) until use.
With the latest advances in vitrification, IVF patients can delay transfers into the future with results almost identical to a fresh embryo transfer. With advanced vitrification, transfers can be spaced out, giving every embryo a better possibility of creating a pregnancy. After the embryos have been vitrified a frozen embryo transfer (FET) cycle can be scheduled for another time in the future. Cryopreserved embryos are preserved in liquid nitrogen for future use for many years as viability of these embryos is maintained intact.
Usual IVF process flow
During an IVF/ICSI treatment cycle the eggs collected from the woman’s ovaries after controlled ovarian stimulation, will be fertilized using her partner’s/donor sperm. Usually between 10 -16 eggs can typically be recovered from the ovary. Those fertilized eggs will be cultured in a specialized incubator to allow their development into embryos. Usually, the best quality embryo is transferred back into the woman’s uterus 3 or 5 days later.( Cleavage stage or Blastocyst stage)
When there is a surplus of good quality embryos remaining these can be selected for cryopreservation (freezing). Not all of these embryos will be deemed appropriate for cryopreservation. Embryos vary in quality – those that are of the best quality are more likely to implant in the womb and lead to a pregnancy. If you have more than one embryo, your embryologist will use their training and expertise to select the best quality embryos using criteria such as the number of cells present , rate of cell division ,whether the cell division is even, whether there are any fragments of cells present – this means that some cells have already degenerated.
A Frozen Embryo Transfer (FET) cycle is then scheduled usually in the next month during a woman’s menstrual cycle. Frozen embryo transfer cycles are relatively simple. Most commonly, the woman takes hormone tablets to prepare the endometrium (lining of the womb). The process is monitored by transvaginal ultrasound scans to identify when the embryo transfer should take place. On the day of embryo transfer, the embryo is carefully thawed and reassessed for its quality. A fine catheter (tube) containing the embryo is carefully inserted into the uterus under ultrasound guidance. The embryo is then placed in the uterine cavity. Two weeks later a pregnancy test is taken.
Steps in an FET cycle include:
- The endometrial lining is first prepared with estrogen.
- Progesterone is started on a selected day which allows synchronization of the uterus with the frozen embryo.
- Prior to the scheduled transfer, the embryo(s) are thawed (warmed).
Freezing embryos followed by an FET cycle provides an IVF patient with an ideal chance of success.
As only good quality embryos are selected for freezing, a frozen embryo transfer has approximately a 60% chance of having a baby. However, the chance of success depends on the quality of the individual embryo. With the introduction of vitrification, frozen embryo transfers have comparable pregnancy rates to fresh embryo transfer. Any patient, no matter the amount of time between embryo freezing and thawing, can expect nearly the same potential for success as they experienced with the fresh IVF cycle that the frozen embryos came from.
Is embryo freezing for me?
One may consider freezing the embryos if:
- You want the option of using your surplus embryos in future IVF or ICSI cycles.
- Your treatment needs to be cancelled after egg collection (for example, if you have a bad reaction to fertility drugs or hyperstimulation like in case of PCOS), or if the uterine lining is matured too earlier than expected or the hormone called progesterone is too high, it becomes rational to freeze all the embryos and plan a transfer later. You should be offered the opportunity to have any suitable embryos frozen to use in a later cycle.
- You have a condition, or are facing medical treatment for a condition, that might affect your fertility (embryo freezing is currently the most effective way for women to preserve their fertility).
- You are at risk of injury or death (for example you’re a member of the Armed Forces and you want to create and freeze embryos with your partner.
- If you’re a female transitioning to a male you may want to preserve your fertility before you start hormone therapy or have reconstructive surgery. Both treatments can lead to the partial or total loss of your fertility
Benefits of embryo freezing
- Cryopreservation process frequently allows couples to save a number of embryos for multiple conception attempts. It also reduces the likelihood that another egg retrieval procedure or use of fertility drugs will be required. If a couple has a baby from an IVF or ICSI cycle and wishes to have a sibling, they do not need to undergo the IVF (ovarian stimulation and egg collection) process all over again. Similarly, if the first cycle is unsuccessful they can opt to use the frozen embryo rather than going through IVF treatment cycle.
- Some couples will have several surplus embryos frozen and therefore enough frozen embryos for more than one subsequent cycle.
- To possibly improve pregnancy outcomes. By delaying a fresh transfer, we can create a more natural physiologic uterine environment
- To avoid possible medical risks of ovarian hyper-stimulation syndrome (OHSS), clinician may choose to freeze instead of fresh transfer in some cases.
- When, for any reason, a fresh embryo transfer is not an option, freezing of embryos is of proven benefit.
- Embryo freezing, specifically, is often an option for people who are trying to get pregnant now through IVF and have more leftover embryos than they’re ready to use right away.
- It’s just as safe as using fresh embryos in treatment.
- Elective single embryo transfer also can be planned and multiple births can be avoided.
- It is a viable option for cases like donor egg IVF where growth of multiple follicles is expected .
- The surplus cryopreserved embryos can be donated for someone else’s treatment, or used for research once due formalities and consent procedures are through.
- It is also a method of fertility preservation due to the fact that the embryo is frozen at a younger age when the woman’s egg, and resulting embryo quality, may be at its best. If you’re having medical treatment that would damage your fertility, such as radiotherapy or chemotherapy, or you have a progressive condition that could affect your fertility in the future, you may want to create embryos with your partner to freeze. If you do this, it’s important to be aware that you or your partner can change your minds at any time about using the embryos in treatment. Embryo cryopreservation is much better option than freezing the Eggs with good success rates of freeze thaw survival.( nearing 99% at Anmol Fertility & IVF Centre)
Are there any shortcomings to embryo freezing?
Not every embryo is a good candidate for cryopreservation . More than 80% of the embryos that are frozen will survive the thawing process. However, this does vary between patients and it’s possible that there is an attrition or none of the embryos will survive the freezing and thawing process. Not all embryos will survive the freezing and thawing process and very occasionally no embryos will survive. It’s not uncommon for those embryos that do survive to lose a cell or two. In many cases the embryo will recover and replace those cells but if they don’t then those embryos won’t be transferred. Use of vitrification technology and advances have largely mitigated such issues and currently the freeze thaw recovery is more than 97% at Anmol Fertility & IVF Centre.
When it comes to IVF treatment in Mumbai, it is important that Before your embryos are frozen it’s very important you give your informed consent by signing the relevant consent forms. These will explain:
- How long you want the embryos to be stored for.
- What should happen to your embryos if you or your partner were to die or become unable to make decisions for yourself.
- Whether the embryos are to be used for your own treatment only, or whether they can be donated for someone else’s treatment, or used for research.
- Any other conditions you may have for the use of your embryos.
During treatment, your doctor will talk to you about various decisions that need to be made regarding your embryos. These include:
- selecting only the best quality embryo(s) for treatment
- whether to put one, two or (very rarely) three embryos back in the womb
- at what stage of development to transfer your embryo(s) back to the womb
How successful is embryo freezing?
Success rates for IVF using frozen embryos have been increasing year on year and are now comparable to rates using fresh embryos. For women aged under 35, birth rates are slightly higher for fresh transfers and rates are level for women aged between 35-37. For women aged over 37, birth rates for frozen transfers have actually exceeded the rates for fresh embryos. This may be because the embryos transferred in the frozen cycle were created using eggs collected some time ago, when the woman was younger. It is noteworthy that embryo cryopreservation is particularly efficient (survival rates of about 97-99%) when the embryos are growing well. As a result, the success of the procedure is intimately bounded to the embryo selection before freezing, the quality control in ART lab and the experience of embryologists in freeze thaw process. The odds of success always are higher if patient is young.
At Anmol Fertility & IVF Centre, our physicians and our entire staff are dedicated to providing a wide range of fertility treatments with excellence. We understand that each couple’s fertility challenges are unique irrespective of the cause of infertility.
It is, however, important to note the following key facts:
- Not all embryos will survive thawing.
- Success rates are comparable to fresh embryos.
- Unused embryos can be discarded or donated.
- Be clear on the legal aspects.
- Embryos are not affected by the length of time they’re frozen for.