What is Embryo Transfer? How is Embryo Transfer Performed?

Embryo transfer is the process of placing embryos, developed in a laboratory setting outside the woman’s body during IVF treatment, into the prospective mother’s uterus. Defined as the fertilization of egg cells collected from the prospective mother with sperm cells taken from the prospective father in a laboratory environment, and then transferring them into the mother’s uterus, embryo transfer can assist couples who are unable to conceive naturally to achieve pregnancy.

What is Embryo Transfer?

Embryo transfer is the procedure of placing embryos obtained during IVF treatment into the uterus under ultrasound guidance by a specialist doctor (1). Infertility, commonly known as sterility, is defined as the inability to achieve a natural pregnancy after 12 months of unprotected sexual intercourse in women under the age of 35, and six months in women aged 35 and older (2). According to research, approximately 15% of couples of reproductive age today experience infertility (3). Thanks to advancements in health technology, various techniques can now be utilized for couples who wish to have children but cannot achieve pregnancy naturally.

Among assisted reproductive techniques, one of the most frequently applied methods today is IVF treatment, known in medical literature as in vitro fertilization. IVF involves collecting egg cells (OPU) from the woman and fertilizing them with a sperm sample from the man in a laboratory environment, then transferring the quality embryos obtained into the woman's uterus. The final stage of IVF treatment is embryo transfer. After embryo transfer, specialists may continue the treatment process by supporting it with various medications to increase the embryo's chance of implantation in the uterus when necessary (4, 5).

How is Embryo Transfer Performed?

In women deemed suitable for IVF treatment, the procedure can be carried out using either a long protocol or a short protocol. The long protocol may extend over multiple menstrual cycles, while the short protocol is typically completed in 2-3 weeks (2, 6).

Under normal conditions, a certain number of egg cells begin to develop during each menstrual cycle in women with regular cycles. However, while one of these eggs matures enough to ovulate, the others are released without maturing. The aim of IVF treatment is to ensure the maturation of all egg cells in that cycle with the help of various hormone medications and injections. This way, instead of obtaining a single mature egg during that menstrual cycle, multiple mature eggs can be harvested.

Medications and injections, known as egg-stimulating drugs, are usually started on the 2nd or 3rd day of the menstrual cycle. Subsequently, specialists will use ultrasound to monitor the size of the follicles (the structures surrounding the egg) and will call the patient to the clinic to check the estradiol hormone levels through blood tests. Typically, when one of the follicles reaches a diameter of 14 mm, another medication is administered to prevent spontaneous ovulation, and when the follicles reach a specific size, the administration of a trigger injection is requested. After this injection, the patient is called to the clinic for the egg retrieval procedure. On the day of egg retrieval, the male partner is also required to provide a sperm sample. In some cases, sperm samples that were previously frozen under special conditions can also be used. The egg retrieval procedure can be performed under general anesthesia or sedation, depending on the patient’s condition and preferences.

Eggs and sperm are combined in specialized laboratories for fertilization. In some cases, it is expected that the sperm will fertilize the eggs spontaneously; however, in patients with insufficient sperm count, a single quality sperm can be injected into the egg using a microinjection technique. Generally, 2-6 days after the egg retrieval procedure, patients are called to the clinic for embryo transfer. If necessary, the obtained quality embryos can be frozen for later transfer (5, 6).

Unlike the egg retrieval procedure, embryo transfer does not require anesthesia. However, in some cases, mild sedative medications may be administered to help the patient feel more comfortable. One or two embryos, assessed by embryologists and containing a small amount of fluid, are placed into a syringe and connected to a flexible catheter. While the patient is in a vaginal examination position, a special speculum is inserted to facilitate access to the uterine opening. The catheter, which holds the syringe, is then advanced towards the uterus (5, 6).

According to the current regulations regarding Assisted Reproductive Technologies and Assisted Reproductive Technology Centers, a single embryo can be transferred in the first and second attempts for women under 35 years old, while two embryos can be transferred in the third and subsequent attempts. For women aged 35 and older, a maximum of two embryos can be transferred in all attempts. This helps to minimize the risk of multiple pregnancies after the procedure (7).

Who Can Undergo Embryo Transfer?

IVF (in vitro fertilization) is one of the assisted reproductive techniques sought by couples diagnosed with infertility who wish to have a child. Some infertility cases arise solely from the woman, while others are solely due to the man. Additionally, approximately 20% of couples diagnosed with infertility have issues stemming from both partners (8). There are also cases of unexplained infertility. For couples with an infertility diagnosis, assisted reproductive techniques such as intrauterine insemination (IUI) or IVF can help achieve pregnancy (9). Embryo transfer can assist any couple in need of IVF treatment for various reasons. The following conditions are suitable for embryo transfer (5):

• Blockage or damage in the fallopian tubes that hinders fertilization or the progression of the embryo into the uterus.
• Ovulation disorders.
• Decreased egg reserve.
• Endometriosis, characterized by the growth of endometrial tissue outside the uterus.
• Male-related causes such as azoospermia (absence of sperm in the semen) or oligospermia (insufficient sperm count and quality).
• The presence of genetic disorders in one or both partners that may potentially affect the health of the future child.

In addition to the conditions listed above, it is also possible to freeze eggs or embryos prior to treatments that may harm reproductive health, such as cancer treatments, and then proceed with transfer (5).

What to Consider After Embryo Transfer?

It is normal to experience complications such as swelling in the groin, mild cramps, and constipation after embryo transfer. Some points to consider following the embryo transfer are as follows (10):

• Using prescribed medications: After embryo transfer, specialists may prescribe medications such as progesterone to increase the chances of the embryo attaching to the uterus. It is important to use these medications as directed by the doctor.
• Maintaining a healthy and balanced diet: Eating a healthy and balanced diet both before IVF treatment and after embryo transfer can enhance the chances of success. It is important to adopt a diet rich in fresh fruits and vegetables, as well as minerals like calcium, magnesium, and iron, and B vitamins. Additionally, incorporating high-protein foods into the diet can help support a healthy pregnancy.
• Taking folic acid: Research shows that taking folic acid, a type of B vitamin, can reduce the risk of congenital heart defects in newborns.
• Avoiding sexual intercourse: Engaging in sexual intercourse after embryo transfer may trigger uterine contractions, potentially reducing the chances of implantation. Therefore, it is advisable to refrain from sexual activity for the period recommended by the doctor after transfer.
• Pregnancy testing: Approximately 10-12 days after the transfer, a blood test for pregnancy can be conducted. Following necessary examinations for those who have been unable to conceive for various reasons, a decision can be made regarding the applicability of IVF treatment. Therefore, it is recommended to schedule an appointment with a specialist to obtain detailed information about IVF treatment and undergo necessary checks.