Reproductive technologies in which egg fertilization takes place in the lab instead of inside the woman's body require the embryos to be transferred back to her uterus. This is the last step of the process in both conventional IVF and ICSI procedures.
Once the fertilization step is completed, the resulting embryos are cultured. During this time frame, embryologists evaluate their quality in order to determine how many and which ones will be chosen and transferred back to the uterus of the intended mother.
Those with the highest quality will be the ones selected. Should there be spare embryos that are viable, they will be cryopreserved for later use using the vitrification technique.
Below you have an index with the 12 points we are going to deal with in this article.
Embryo transfer consists of depositing the embryos generated in the laboratory into the mother's uterus while waiting for them to implant and give rise to a pregnancy. It is a simple and painless process that does not require anesthesia.
Normally, the embryo transfer is carried out in a room attached to the laboratory to avoid risks in the handling and transport of the embryos.
The success of the embryo transfer does not depend only on the quality of the embryos, but it is also important to evaluate the state and receptivity of the endometrium. In addition, the technique must be correct and it is always checked in the laboratory that the embryo has not remained in the transfer cannula.
When to perform the embryo transfer?
The day on which the embryo transfer should be carried out is decided by the specialists, analyzing each case personally. It is important to take into account the quantity of embryos, their quality, the state of the endometrium and the results of previous IVF cycles.
To increase the success rate of the embryo transfer, it is essential that the endometrium be prepared, i.e. that it is receptive to increase the probability of embryo implantation. For this purpose, the patient is given medication to stimulate endometrial growth.
Therefore, embryo transfer can be performed at any time of embryonic development, as long as the endometrium is receptive. There are centers where the transfer is done in zygote state, on day 2 or in morula stage. However, the most usual is to do the embryo transfer on day 3, in the early embryonic stage, or on day 5, in the blastocyst stage. Both moments offer their advantages and disadvantages.
More information on this topic here: Day 3 vs. Day 5 Embryo transfer.
Types of embryo transfer
Sometimes, the embryo transfer is not carried out at the same time as fertilization in the laboratory and the embryos are vitrified without altering their quality. For this reason, two types of embryo transfer can be distinguished according to whether the embryos are frozen or not:
- Fresh transfer: the embryos are fresh and are transferred in the same cycle in which they were created, without being frozen.
- Frozen transfer: The embryos are frozen for transfer in another cycle. This transfer is also called cryo-transfer or frozen embryo transfer. This type of transfer is used when it cannot be transferred in the same cycle in which the puncture was performed. An example in which this transfer is necessary is in the case of ovarian hyperstimulation.
For more information on when and how the frozen embryo transfer is done, access this article: How Does the Frozen Embryo Transfer (FET) Procedure Work?
Embryo transfer Step by Step
IVF embryo transfer is a simple technique whereby embryos are placed in the uterine fundus of the mother-to-be using a thin catheter, which is inserted vaginally and reaches the uterus through the cervix.
Generally, the specialist performs it guided by an ultrasound in order to place the embryos in the right site. In the past, gynecologists used to do it without the guidance of an ultrasound, but today it has been demonstrated that it helps achieve better results, simply because it allows to place the embryos in the uterine fundus more accurately.
Simply put, the embryo transfer procedure involves the following steps:
- A sterile speculum is placed in the vagina
- The vagina is cleaned with physiological saline solution
- The cervix is cleaned with culture medium and cervical mucus is aspirated
- The embryos are placed in the catheter
- The catheter is inserted vaginally through the cervix till it reaches the uterus
- The embryos are gently placed in the uterine fundus
- The catheter is removed gently and slowly from the vagina
The process takes a few minutes and does not require anesthesia or sedation. Although the patient may feel little discomfort, it is a painless procedure. Only if the transfer becomes complicated, that is, if inserting the catheter through the cervix becomes a challenging step, the transfer may be painful. If that were the case, your gynecologist would try with a different type of catheter until he or she can reach your uterine fundus easily. Sedation is used in extreme cases only.
After the embryo transfer, you can leave the clinic after a 20-30 minute rest at the clinic. You can continue with your normal life, avoiding excessive efforts, though.
Embryo transfer medications
When it comes to performing an embryo transfer, there exist two possible options:
- Natural cycle
- Without using artificial medication or just with progesterone supplements. IVF/ICSI cycles are rarely done without progesterone.
- Stimulated cycle
- Using hormonal medications. Estrogen and progesterone are used to prepare the endometrial lining.
Medication should be administered both before and after the embryo transfer, following the doctor's instructions at all times.
Tips for the embryo transfer day
The following are some recommendations for the day of the embryo transfer:
- Come in with a full bladder
- It eases the transfer process to a large extent. With an empty bladder, inserting the catheter may become more challenging due to the input angle that forms.
- Just relax
- If your muscles are tense, the process becomes easier. When patients are too nervous, a muscle relaxant may help.
- Don't use perfumes, lotions or nail polish
- These chemical products should be avoided, especially at the operating room, transfer room, and the lab, since they are toxic for the eggs and embryos.
Contrary to common belief, fasting is unnecessary—an embryo transfer is not a surgical procedure.
In spite of all this, and as confirmed by Dr. Àlex García Faura, gynecologist specialized in Reproductive Medicine, the majority of patients live the embryo transfer day with anxiety. In fact, they feel tense and restless during the previous days as well, especially while the embryos are being cultured.
Finding out whether the resulting embryos will be viable and have good quality is an aspect that generates great distress amongst patients.
The good news is that today, thanks to state-of-the-art systems like EmbryoScope, patients can see the development of embryos on a day-by-day basis, thereby reducing their stress levels.
After the embryo transfer, experts recommend:
- Rest at the clinic for 20-30 minutes
- Avoid immersion baths to prevent infections
- Continue with normal lifestyle avoiding excessive efforts
- Drink plenty of water
- Abstain from sexual intercourse until pregnancy test day
Visit your doctor in case of any doubt.
Get more info by clicking the following link: Post Embryo Transfer Tips & Precautions – What Should You Expect?
An embryo transfer may be canceled in case there are no embryos to transfer or if the embryo was unprepared for implantation.
These two situations may lead to the absence of embryos to transfer:
- Fertilization failure
- No oocyte is fertilized, and subsequently there are no embryos.
- Embryonic arrest
- Due to the presence of genetic abnormalities or alterations of embryo development. It is more common with blastocyst culture.
In these cases, an IVF cycle must be started anew in order to do an embryo transfer.
If the uterine lining is not ready to receive the embryos and allow them to attach, the embryos will be frozen and transferred in subsequent cycles, that is, a FET would be the type of transfer carried out.
Related article: IVF Cancellation Reasons - What Happens If IVF Cycle Is Cancelled?
Quality and origin of the embryos
We can use both good and poor quality embryos for the embryo transfer. Those of exceptional quality have an increased implantation potential, and therefore the pregnancy chances will be higher. These are four embryo grading systems as established by the ASRM (American Society for Reproductive Medicine):
- Grade I
- top quality embryos
- Grade II
- Good quality embryos
- Grade III
- Fair quality embryos
- Grade IV
- Poor quality embryos. Likelihood of implantation is very low.
It should be noted that if the embryos are donated or come from donor eggs, they are usually of good quality and have a high probability of being implanted.
Recommended reading: Embryo Quality & Grading.
In case they are donated embryos or have been created using donor gametes, they will be grade I in most of the cases, which translates into high chances of success.
How many embryos to transfer
Most fertility clinics recommend single or two embryo transfers in order to reduce the probability of multiple pregnancy. In any case, however, determining the amount of embryos to transfer is not easy, since it depends on several factors, among which we highlight the following:
- Age of the patient
- Embryo quality
- Characteristics of the uterus
- What is causing infertility
- Embryo cryopreservation methods effectiveness
There is an increasing number of specialists that recommend single embryo transfers in order to reduce the chances of getting pregnant with twins or more. It should be reminded that this type of pregnancy carries a number of risks for both the mother and the babies.
Many countries have established limits regarding how many embryos to transfer. In Spain, the law limits this amount to a maximum of 3 embryos, even though experts tend to recommend single embryo transfers. By doing this, we can reduce the chances of getting pregnant with multiples, which involves a greater number of risks.
Read this next: How Many Embryos Should You Transfer for IVF?
What is the fate of unused embryos?
Only the embryos considered optimal under the embryologist's criteria are used for the transfer. However, there may be top quality embryos that are not used, in which case they will be cryopreserved (frozen) indefinitely. Thanks to this, they can be used in subsequent cycles.
If pregnancy occurs and the woman wants to have more children in the future, these cryopreserved embryos can be used for a new IVF cycle. The main advantage is that she would not have to start a complete IVF cycle again, but just take the medications that are necessary to prepare the endometrium for a new transfer.
There are cases where the patient or couple does not wish to have more children. The spare embryos can be donated to other couples or for stem cell research as long as they agree to sign an informed consent.
In some countries like Spain, embryos cannot be destroyed until the woman's reproductive years have come to their end, that is, at age 50 approximately. In other words, if she does not want to use them or donate them, she will have to keep them stored in liquid nitrogen.
Click here to read more: What Is the Fate of Unused IVF Embryos?
What is the cost of a FET?
A FET is the option of choice when a patient needs to do a second attempt after a failed cycle, or when she wishes to have a second child using the spare embryos from previous cycles.
The cost of a Frozen Embryo Transfer in the United States averages anywhere from $3,000 to $5,000 per cycle. In the UK, on the other hand, the common fee is £1,400.
Fertility treatments, like any other medical treatment, require that you trust the fertility specialists that will be by your side during your journey. Logically, each clinic has a different work methodology. Our Fertility Report will offer you a selection of recommended clinics, that is, fertility centers that have passed our rigorous selection process. Moreover, our system is capable of comparing the costs and conditions of each one so that you can make a well-informed decision.
Some clinics offer shared risk 100% refund programs for FET, which allow patients to pay a flat fee for unlimited FET cycles for as many frozen embryos as that patient may have available. This does not include the fees for medication, which usually range between $400 and $800.
After embryo transfer
After the embryo transfer, having menstrual pains is unusual, embryologist Aitziber Domingo Bilbao states. However, they can have a brownish or pinkish spotting that is due to the passage of the catheter through the vagina.
According to Aitziber Domingo, it is more common for patients to have premenstrual symptoms. Indeed, they can be due to two causes: because their period is about to show up, or because actually they are pregnant and they are actually early pregnancy symptoms, like swollen breasts, abundant vaginal discharge, etc.
She recommends that you continue with your normal lifestyle, but avoiding major efforts such as attending dance classes, for example. Not because it can affect embryo implantation, but actually for the psychological impact these activities can have on the patient, especially if they get a negative result.
FAQs from users
I have a history of recurrent miscarriage, when should the embryo transfer be done in my case?
The fact that a woman has had repeated miscarriages in the past has nothing to do with the day of the embryo transfer. In most of the cases, it is associated with the chromosomes of the embryos. Keeping this in mind, ideally the best treatment option in these cases would be IVF with PGD (Preimplantation Genetic Diagnosis). With PGD, we examine 6-8 cells of each embryo. It allows us to find out which embryos are genetically norma and which don't.
What are the advantages of transferring on day 5 compared to day 3?
Existing evidence shows that culturing embryos till stage 5-6 of development, we can increase the pregnancy success rates per fresh and frozen embryo transfer. This is due to the fact that the embryos to transfer or cryopreserve can be selected more properly, since blastocysts have a higher implantation potential. It also improves embryo-endometrial synchrony.
One should keep in mind that about 50 percent of viable embryos will arrest on day 3 of development. In other words, they will not make it to blastocyst stage.
Can the success rate of IVF be increased with a 3-embryo transfer?
The greater the number of embryos transferred, the higher the chances for at least one of them to implant, thereby achieving the ultimate goal of IVF: a pregnancy. Nevertheless, by doing it, the likelihood of getting pregnant with twins increases too, which would entail a higher number of risks than a singleton pregnancy.
To sum up, except under special circumstances, specialists do bet on elective single embryo transfers (eSET), which consists in selecting the embryo with the best quality for the chances of implantation to be increases without the need for a multiple embryo transfer.
What are the day-by-day symptoms after an embryo transfer?
As explained earlier, IVF embryo transfer is a simple procedure which presents no severe symptoms or side effects at all. Once the embryos have been placed into the uterus and the woman has rested for a few minutes right after that, she can continue with her normal lifestyle.
Strong pain or severe adverse reactions are uncommon. However, there are cases in which women may develop a mild discomfort or slight bleeding as a consequence of cervical manipulation at the time of embryo transfer.
On the other hand, there are no ET failure symptoms. While some women may experience nausea, bloating or even spotting/bleeding due to hormone medications or embryo implantation, these side effects can be noticed as well without it indicating success or failure.
How can I prepare for my IVF transfer day? What are the best tips to turn it into a success story?
The best tip for achieving success after an ET is being relaxed at the very moment when the procedure is to be performed.
Besides, having a full bladder is strongly advisable, as it is a way for the doctor to observe your uterus through ultrasound in a better way. It allows for the doctor to place the embryo in the adequate location, without scratching the lining of the womb.
On the other hand, there are no "implantation foods" to boost your chances of becoming pregnant. If so, your clinic would prescribe them to you.
In fact, fixating on specific foods may cause more harm than good. Experts do recommend to follow a balanced diet from at least 3 months before your treatment starts. Avoiding processed foods, limiting your sugar, eating good carbohydrates, etc. could be beneficial.
Is there any after-care plan to follow after embryo transfer?
Firstly, it should be clear the total bed rest after an ET is unnecessary and can be counterproductive. It has been proved that bed resting for recovery does not increase the pregnancy rates.
In fact, being totally sedentary may be a disadvantage, as inactivity and high levels of estrogens can promote blood clotting and a rise in insulin resistance.
Doing exercise and leading a normal lifestyle is beneficial, as it can help reduce inflammation and cramping by promoting healthy blood flow and lowering the levels of stress.
When should I take a pregnancy test after a donor-egg embryo transfer?
Like in any other IVF procedure, after an embryo transfer with donated eggs, women have to go through the two-week wait or 2WW, a time period necessary for beta-hCG levels to be detectable by a pregnancy test.
The presence of the hormone hCG in blood increases gradually from embryo implantation up until the end of the third trimester approximately. This, along with other hormonal changes, is the reason why the common pregnancy symptoms appear (nausea, vomiting, etc.)
When will I be able to find out whether the result of my embryo transfer is positive?
In general, women should wait for between 10 to 15 days after the embryo transfer to take a pregnancy test. From that moment on, we can confirm whether embryo implantation has been successful, that is, if the woman is pregnant or not.
What is an embryo transfer from one woman to another?
It refers to embryo donation and adoption, a technique which involves donating your unused embryos after an IVF cycle to another woman.
Suggested for you
There exists other type of embryo transfer known as Intratubal Embryo Transfer (IVF/IT-ET) or Zygote Intrafallopian Transfer (ZIFT), in which the fertilized eggs (zygotes) are placed in the Fallopian tube. Find more information about this option here: What Is Zygote Intrafallopian Transfer (ZIFT)?
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FAQs from users: 'I have a history of recurrent miscarriage, when should the embryo transfer be done in my case?', 'What are the advantages of transferring on day 5 compared to day 3?', 'Can the success rate of IVF be increased with a 3-embryo transfer?', 'What are the day-by-day symptoms after an embryo transfer?', 'How can I prepare for my IVF transfer day? What are the best tips to turn it into a success story?', 'Is there any after-care plan to follow after embryo transfer?', 'When should I take a pregnancy test after a donor-egg embryo transfer?', 'When will I be able to find out whether the result of my embryo transfer is positive?' and 'What is an embryo transfer from one woman to another?'.