Single Embryo Transfer

Single embryo transfer at a glance

  • A single embryo transfer (SET) is the process of transferring one high quality, blastocyst stage embryo during an IVF treatment.
  • Single embryo transfers are preferred over multiple embryo transfers because they drastically reduce the risk of a twin pregnancy, which carries additional risks for the children and mother.
  • Recent advances in fertility medicine have raised the chances of becoming pregnant with a single embryo transfer to almost the same level as with a multiple embryo transfer.

What is single embryo transfer?

Single embryo transfer (SET) is the process of implanting one, high quality embryo into a woman’s uterus during in vitro fertilization (IVF). In the past, transfer of single embryos was rarely practiced because the chances for pregnancy were significantly higher if two or more embryos were transferred.

Comparable pregnancy success rates through single embryo transfers can only be achieved with a superior IVF laboratory that can support the growth of blastocyst stage embryos. Our lab has this capability, offering patients the SET option that competes with pregnancy rates obtained when transferring two or more embryos.

A blastocyst stage embryo is an embryo that has developed for 5-6 days, has two distinct cell types that have started to differentiate (one becomes the fetus, one becomes the placenta), and a fluid filled central cavity. During natural conception an embryo is fertilized at the end of the fallopian tube closest to the ovary that released the egg and travels for 5-7 days through the Fallopian tube before implanting in the uterus. Transferring a blastocyst stage embryo during IVF gives the embryo the best chances of implanting in the uterus. This is because an embryo that has been conceived through sexual intercourse typically implants at this stage as well.


Who should consider single embryo transfer?

  • Certain criteria indicate higher chances of success with single embryo transfers. If a woman is 37 or younger and has produced a high-quality embryo (blastocyst stage), she is a great candidate for single embryo transfer.

Frisco Institute for Reproductive Medicine has a live birth rate around 70 percent, with a twin rate of  <1 percent, when the above criteria are met during a single embryo transfer IVF cycle.

Couples with a high likelihood of having twins when transferring two embryos should seriously consider transferring a single blastocyst stage embryo. These couples include:

  • Women age 37 or younger
  • Couples using donor eggs
  • Any woman whose doctor advises that she may be at increased risk to have a miscarriage or medical complications when becoming pregnant with twins.

Many couples repeat the mantra “two is better than one,” thinking that two embryos give a greater chance for pregnancy, or that two babies from one IVF cycle would complete their desired family with one pregnancy.

While many people believe that the risks associated with multiple pregnancy(twins or more) are minimal and manageable, the medical community has well established that a twin pregnancy poses significant risks to the mother and babies. Additionally, multiple births have a significant financial and psychological impact on the prospective parents and their families.

Due to the numerous complications that a high-risk multiple pregnancy can have, fertility doctors and laboratory directors have been improving the in vitro fertilization process so pregnancy rates from a single embryo transfer are almost as high as with a multiple embryo transfer. Preimplantation genetic screening can further increase the chances of pregnancy with a single embryo transfer by only transferring an embryo that is free of genetic or chromosomal defects.


What are the benefits of single embryo transfer?

The largest benefit of single embryo transfer is an astounding reduction in twin rates, from 67 percent to only about 1 percent. Couples will also have the option of freezing at least one blastocyst embryo for future use.