Overview of Selective Embryo Transfer (eSET)
- Posted on: Feb 18 2016
Selective embryo transfer (SET) is an option for many couples who are at risk for transmitting an inherited condition. After embryos are produced via standard in vitro fertilization (IVF) techniques, 1-2 cells are removed from each embryo to evaluate the disorder. Each embryo has only 6-10 cells, so removing one will not bring harm. Only embryos proven free of the disorder will be transferred. In addition, SET eliminates the risk for multiple pregnancies.
In 2000, more than 66% of all IVF procedures in America involved 3 or more embryos. This led to a rise in multiple pregnancies. Because of some concerns, to the mother and unborn children, fertility specialists started using SET. The technological advances with IVF and selective embryo transfer pose certain serious ethical issues. With SET, it is possible to determine the sex of the embryos, which can lead to sex selection. Most experts and fertility specialist are not happy with the concept of sex selection for non-medical reasons.
Benefits of Selective Embryo Transfer
Patients who are attempting pregnancy using IVF may have more than one embryo available for transfer. However, use of multiple embryos increase the risk of multiple births (twins, triplets, or quadruplets). Multiple births can lead to low birth weight infants, preterm birth, and long-term health conditions, such as hearing loss, vision loss, cerebral palsy, and autism. In addition, multiple births pose serious health risks to the mother.
Recent clinical studies show that elective selective embryo transfer improves a woman’s chances for a successful pregnancy. Improvement of freezing techniques for embryos has allowed higher pregnancy rates as well. In the 1990s, frozen embryo success rates were around 10% per embryo. With advancement in freezing techniques, use of frozen embryos have the same pregnancy rate today as using fresh embryos for transfer.
The trend for transfer of multiple embryos is declining, according to research from 1999 to 2008. Researchers have seen the proportion of multiple embryo transfers drop from 70% to 39%. Each year since 2002, selective embryo transfer rates for women age 35 and younger has increased. Today, SET accounts for 10-20% of all transfers in this age group.
Factors for Favorable Prognosis
According to the American Society for Reproductive Medicine (ASRM), elective single embryo transfer yields a favorable prognosis for women who are 35 years of age and younger. For women over the age of 35 years, a maximum of 2 embryos should be transferred. However, for all women, certain factors must be considered. These include:
- The age of the woman
- Her day 3 laboratory test results
- The cause of the couple’s infertility
- The number of embryos available for transfer
- Quality of the embryos available
One factor that could influence how many embryos to transfer is if the woman has a uterine anomaly, which would increase the risk for preterm birth. If the mother has certain medical conditions, the condition could be aggravated from twin pregnancies. Good quality embryos are less likely to result for older women. Therefore, ASRM guidelines encourage 2-3 embryos in the transfer for women 35-37 years of age, and 3-4 for women 38-40 years. However, SET should be used if the couple wishes to decrease the risk of multiple pregnancies.
Risks of Multiple Embryo Transfers
When multiple embryos are transferred, the woman has an increased risk for twins, triplets, or more (multiple pregnancies). Carrying more than one baby can lead to serious complications for both the mother and the unborn children. Multiple births are associated with lung problems, intellectual disabilities, need for a cesarean section, and extended recovery after birth. For the mother, there is a risk of gestational diabetes, heart problems, iron deficiency anemia, pre-eclampsia, placenta previa, and preterm labor.