Elective Single Embryo Transfer (eSET)
Elective single embryo transfer at a glance
- Elective single embryo transfer (eSET) occurs when a parent(s) undergoing in vitro fertilization (IVF) elects to transfer only one of several good quality embryos available.
- In high prognosis patients, eSET is recommended by the American Society for Reproductive Medicine and the Loma Linda University Center for Fertility to reduce the chance of a multiple pregnancy (twins or more), which happens more often when more than one embryo is transferred.
- In the past, transferring more than one embryo in the majority of IVF cases was routinely done to improve success rates.
- Mothers of multiple births face health risks, as do the children, including low birth weight, preterm birth and health conditions such as learning problems and cerebral palsy.
- Not all women are good candidates for eSET, and not all single embryo transfers are “elective.” In some cases there is only one embryo available from the IVF procedure, or insurance restrictions limit the transfer to just one embryo.
What is elective single embryo transfer (eSET)?
When an individual or couple has more than one high-quality embryo created with IVF and chooses to transfer only one embryo, this is referred to as an elective single embryo transfer (eSET). The transfer of one embryo reduces the chance of a multiple pregnancy but in some cases, the chance of pregnancy is also reduced.
About 20 to 25 percent of deliveries in the United States via IVF are twins, with 3-4 percent involving triplets or more. By contrast, 3.39 percent of naturally conceived births in the U.S. were twins, according to 2014 Centers for Disease Control figures.
In the past, transferring two or three embryos was the routine practice in most IVF cases. This was because rates of successful implantation were low when transferring only one embryo. But as those rates have increased with improvements in the IVF process, and with improved cryopreservation of the remaining healthy embryos, fertility specialists reassessed the practice of multiple embryo transfer.
The result is a growing commitment in the field of fertility medicine to transfer the minimal number of embryos that can reasonably be assumed to result in pregnancy. The consensus now is that the preferred outcome of assisted reproductive technologies is a healthy singleton child.
The word “elective” is key. Single embryo transfer is mandatory in some countries, as long as the prognosis is good for the particular patient. That is not the case in the U. S. and it is not unusual for patients and couples that are good prospects for eSET to decline to transfer only one embryo, even if encouraged to do so by their fertility physician.
Usually, the reason for this is that multiple transfer increases the odds of at least one child. At Loma Linda University Center for Fertility, we encourage eSET for patients who are good candidates. But we also respect the wishes of the person/couple making that choice. This is where the medical issue of patient autonomy, allowing patients to make treatment choices based on their values, bumps up against the doctor’s desire to reduce health risks, in this case due to multiple births.
This is understandable on the patient’s part, as success rates of birth with fresh cycle eSET are around 26 percent compared with a 43 percent success rate for births with fresh cycle double embryo transfer, according to ASRM. Cost may be another factor inhibiting people from eSET, as the prospect of multiple IVF cycles significantly increases patient costs.
But as the success of frozen embryo transfer improves, so does the success rate of eSET. Today, the success rates for transferring frozen and fresh embryos are about the same. If a couple knows they have several other viable frozen embryos that can be used later, they may be more apt to go with eSET on the first transfer.
Many patients and couples only have one embryo after IVF. They do a single embryo transfer by default, as they have no other option. The pregnancy success rate in these cases is low.
Candidates for elective single embryo transfer (eSET)
It is important to note that not everyone is a good candidate for elective single embryo transfer. Fertility specialists will review these issues with each patient. eSET should be selectively used on patients with the best prognosis for eSET success, based on the patient’s reproductive characteristics and on the embryo(s) quality.
Factors women possess that relate to good prognosis include:
- Being under age 35, as their egg and embryo qualities are usually better than in older women
- Having more than one top-quality embryo available, as the quality is more important than the quantity
- Have had success with IVF before
- Are undergoing their first IVF cycle
- Using embryos from donated eggs.
Fertility physicians generally like to transfer embryos when they are at the day 5 blastocyst stage because the embryo selection process is improved when the embryo is further along in development. At this stage of development, the embryo has two cell types, one for the fetus and one for the placenta, indicating that it has a better chance of successful implantation.
Health risks of multiple pregnancies
Simply put, a multiple pregnancy involving twins, triplets or more is dangerous for the mother and child, increasing the risk of death and disease. Dangerous health risks for the mother are preterm labor and delivery, gestational diabetes and preeclampsia (a pregnancy complication involving high blood pressure and potential damage to organs). For comparison, 15 percent of singleton births are preterm and 40 percent of twin births are preterm – 75 percent for triplet births.
Other complications of multiple pregnancy for the mother, most of which are related to preterm labor and delivery, include:
- Gaining excess weight
- Skin diseases
- Cholestasis, a liver condition reducing or stopping the flow of bile
- Problems with the abdominal wall
- Umbilical hernias
- Increased reflux and constipation
- Chronic back pain
- Severe nausea.
Health risks to the fetus and baby can be serious. Fetal death, though low in occurrence, is still three times higher for twins than for a singleton birth. Reduction in birth weight, a major indicator of ongoing medical problems for a child, are almost tenfold for twins and more for triplets.
Following are the most common problems children face when they are born preterm (“preemies”).
- Immature lungs, a major concern in preterm babies resulting in various conditions such as recurrent pneumonia and respiratory distress syndrome that causes difficulties breathing and may require the newborn to be on a respirator
- Susceptibility to infections
- Bleeding in the brain (intraventricular hemorrhage), which can lead to cerebral palsy and intellectual and developmental disability
- Difficulty maintaining body heat
- Stomach and digestive problems
- Cardiac disorders
- Sepsis, which is bacteria in the blood
- Potential blinding disorders (retinopathy of prematurity).