Embryo transfer is the process of placing embryos into the uterus following egg retrieval. Factors such as the quality of embryos, the age of the patient, and the number of IVF attempts are considered in the transfer. The selection of embryos and the number of embryos to be transferred are personalized based on individual circumstances. Genetic tests can be used to assess the health status of embryos, but they are controversial in cases such as advanced age or recurrent pregnancy loss.
Between the 2nd and 6th day after egg retrieval, embryos are transferred to the uterus via a thin catheter under ultrasound guidance. The most suitable embryos that have completed the division stage are preferred for transfer.
To avoid trauma during embryo transfer, a mock transfer before the actual transfer can reduce the likelihood of a difficult transfer. In cases of difficulty during transfer, all embryos can be frozen, and after identifying and treating the cause hindering the transfer through hysteroscopy, embryo transfer can be planned for another cycle.
The patient is prepared for transfer through a gynecological examination. The vagina and uterine cervix are cleaned with sterile solutions. With the guidance of an ultrasound screen, the catheter carrying the embryos is inserted into the uterine cavity. After releasing the embryos into the most suitable part of the endometrium using a syringe, the catheter is slowly withdrawn.
The selection of embryos with the highest potential for pregnancy (the number of embryos and at which stage of development they will be transferred) is based on several criteria:
The age of the patient, the reason for IVF treatment, and the number of treatment attempts are essential factors.
Predicting the number of embryos that will form based on the number and quality of eggs obtained through treatment is challenging. Therefore, these criteria need to be highly personalized.
The number of embryos to be transferred is usually 1-2. The decision is influenced by the woman's age, the quality of embryos, and previous IVF attempts. In our country, regulations allow the transfer of a maximum of 2 embryos under the age of 35 in the first 2 IVF attempts, and then 2 embryos in subsequent attempts. For women aged 35 and above, regardless of previous IVF attempts, a maximum of 2 embryos can be transferred.
The choice of transfer day is individualized. Embryo transfers can be performed on the 2nd-3rd or 5th day after embryo formation. Although transferring embryos at the blastocyst stage (5th day) is ideal, embryos that do not reach this stage but still result in pregnancy on the 2nd and 3rd days can also exist.
Being visually healthy does not mean embryos are genetically normal. Therefore, if there is a known structural or single-gene disorder transmitted from the mother or father at the beginning of treatment, embryo selection free of the disease can be made through genetic analysis of the embryo material.
In cases of advanced maternal age, recurrent pregnancy loss, or repeated miscarriages, genetic screening in embryo selection is a controversial topic.
Embryo transfer is one of the most critical stages of IVF treatment and should be carefully planned for a successful pregnancy. The number of embryos to be transferred, the developmental stage of the embryo, and factors such as the patient's medical history should be considered, and an individualized approach should be adopted. Genetic tests can be applied if necessary, but they are not mandatory for every patient. Successful embryo transfer is achievable by applying the correct techniques and considering individual factors.
