Embryo transfer (ET) is the next-to-last step involved in the in vitro fertilization (IVF) process, only followed by pregnancy testing. Given that it is a simple and painless technique, taking time off and special care are not needed. It can be done with own or donated embryos, fresh or frozen, on day 3 or on day 5.
Once the ET is done, the only thing left to do is waiting for embryo implantation into the uterine lining, i.e. endometrium, to occur. In other words, implantation of the embryo means pregnancy would have occurred. Thus, from this moment on, the success of the fertility treatment will depend solely on the embryo’s ability to attach to the endometrial lining of the uterus.
Process, timeline and due date
As explained earlier, ET is not a painful procedure, and therefore sedation/anesthesia is not required. It takes only a few minutes and can be done either at the operating theater or the gynecologist’s office.
It involves two steps:
Preparing uterus for embryo transfer
To increase the chances for the transferred embryo or embryos to implant, the endometrial lining should be adequately prepared for embryo implantation, which depends fundamentally on two factors:
- Uterine lining thickness of around 7 and 10 mm
- Triple line endometrial pattern
Endometrial receptivity can be achieved with hormone therapy, administered to the patient through oral, vaginal or patch route. The type of medications given depend on the particularities of each situation:
- Egg donation: Patients take estrogens and progesterone, regardless of whether it is a fresh or frozen egg donor cycle.
- IVF with fresh own eggs: Estrogens are not usually administered, so the treatment is only based on progesterone medications.
- IVF with frozen own eggs: Since follicle puncture was carried out in a previous cycle, both estrogens and progesterone are necessary to achieve the required uterine receptivity for implantation.
- Embryo adoption: Both estrogen and progesterone are used.
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It should be clear that the above mentioned are general protocols, which means they may vary from patient to patient. For example, even though it is uncommon, there are cases where the ET is done with frozen embryos in a natural cycle as a way to use the estrogens released in a natural way.
Embryo transfer day
Aided by a thin catheter, the embryos are inserted into the uterus through the cervical canal. Once the embryos are placed in the fundus of the uterus, the catheter is removed. Special attention should be paid both when inserting and removing the catheter, otherwise the uterine wall may be damaged.
After embryo transfer, the woman should rest for at least 10 minutes and not longer than 20 min. Then, she can get back home and continue with her normal lifestyle.
Finally, women can test for pregnancy on day 15 post embryo transfer approximately. In case you get a negative result, medications prescribed for the preparation of the endometrium will be no longer necessary.
How many embryos to transfer
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
After analyzing the above mentioned factors, the number of embryos to transfer will be established, always with the ultimate goal of turning the fertility treatment into a successful one without increasing the chances of getting pregnant with multiples, which would put both the fetus and the mother at risk.
Many countries have established limits regarding how many embryos to transfer. In Spain, for instance, 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.
Day-3 vs day-5 embryo transfer
Embryos can be transferred at any moment of their development from day 1—as soon as fertilization is confirmed—to days 6 or 7. Nevertheless, embryo transfers are often carried out on days 2-3 or 5-6, since these are the best moments for their quality to be properly and easily assessed.
Choosing between one day or another will depend not only on the patient’s preferences or the methodology followed by each clinic, but also on the need for additional techniques such as preimplantation genetic diagnosis (PGD) or embryo cryopreservation.
Studies on what is the best moment for the transfer are often contradictory; while some experts are in favor of day-3 embryo transfers (cell stage), others have a preference for doing it on day 5, when the embryo is at blastocyst stage.
The moment when the embryo changes from being at cell stage to blastocyst stage is a critical one, as its viability could be compromised, which would lead to the cancellation of the transfer. This is the reason why some embryologists are in favor of day-3 transfers.
On the other hand, day-5 transfers allow for the selection of the highest-quality embryo with the best judgement. By choosing the best, we raise the success rate of single embryo transfers (SET), while reducing the need for using two embryos. Transfers on day 5 make the process more similar to natural implantation, which improves the synchronization between the woman’s physiological state and endometrial receptivity.
FAQs from users
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.
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.
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 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.