Elective Single Embryo Transfer (eSET)
eSET at a glance
- Elective single embryo transfer (eSET) is when a woman or couple decides to voluntarily implant a single embryo during in vitro fertilization (IVF), even when multiple viable embryos are available.
- Improvements in technology and a rise in concern over the risks of multiple birth pregnancies have led to an increase in women and their partners opting for eSET.
- The American Society for Reproductive Medicine (ASRM) has established that the goal of assisted reproductive technologies should be a healthy singleton pregnancy, emphasizing the need for eSET.
- A multiple pregnancy (twins or more) increases health risks for mother and babies, including the inability to carry fetuses to full term, premature birth, low birth weight, developmental disabilities and cesarean section delivery.
What is elective single embryo transfer?
Elective single embryo transfer, or eSET, is when a woman and her partner decide to voluntarily implant only one embryo, even when multiple viable embryos created via in vitro fertilization (IVF) may be available for transfer. The embryo is carefully chosen based on a number of factors, sometimes with the aid of preimplantation genetic testing that can identify embryos without genetic defects, resulting in better pregnancy and birth success. Embryos that are not implanted may then be cryogenically frozen and preserved for future use.
Because women undergoing IVF are given medication to stimulate egg production, often more than one egg will be successfully fertilized, at which point they become embryos that can be implanted in the uterus.
In the past, transferring multiple embryos during an IVF cycle was standard practice for the majority of patients. As technology and implantation rates have improved however, this need to transfer multiple embryos in order to achieve a successful pregnancy has largely decreased.
In addition, health concerns that accompany multiple birth pregnancies have led to a reassessment of the multiple embryo transfer approach. For many IVF recipients, the benefits of single embryo transfer may outweigh the potential benefits of transferring multiple embryos.
Why choose eSET?
The primary reason patients choose eSET is to reduce complications that accompany multiple birth pregnancies. However, not all IVF patients have more than one embryo to transfer, so they have no “elective” option to transfer a single embryo.
According to ASRM, 30 percent of IVF pregnancies in the United States are twin pregnancies and 3 to 4 percent are triplet or higher. Giving birth to two or more infants puts both the mother and babies at greater risk for medical complications. According to the Centers for Disease Control and Prevention, multiple births increase the risks for:
- Premature birth
- Low birth weight
- Developmental disabilities
- Cesarean section delivery
- Inability to carry some or all fetuses to full term, sometimes leading to the need for fetal reduction procedure. This can be an emotionally and psychologically trying scenario that involves aborting one or more fetuses in order to increase the chances of carrying one to full-term.
ASRM and The Society for Assisted Reproductive Technology (SART) have conducted extensive research that has led to guidelines stating that eSET should be considered for patients who are 35 years of age or younger and are able to produce quality embryos. These guidelines are by no means hard and fast rules however, and patients should work in consultation with their physician to arrive at a course of action based on their specific situation, concerns and needs.
eSET risks and considerations
While eSET is an appropriate option for many IVF patients, there are a number of factors to consider. In addition to the ASRM/SART guidelines above, the best candidates for eSET are generally women who:
- Have produced embryos that can be preserved for future use
- Have had success in past IVF cycles
- Are undergoing their first IVF cycle.
Even if a woman is over 35 or does not have a favorable prognosis for producing quality embryos, other factors may also lead to the decision to implant a single embryo. For example, if a woman has a pre-existing condition that would be complicated by a multiple birth pregnancy, single implantation may be advised.
Regardless of age and the other factors outlined above, the option for eSET should remain open to any woman wishing to minimize the risk for multiple birth pregnancies and the associated complications.