COVID-19 Information

All for One: Why We Advocate for Single Embryo Transfers

Written By: Women & Infants Fertility Center on July 24, 2017


Let’s face it: Twin babies are cute. The matching outfits, the double-wide strollers, the shared birthday parties…I’d be lying if I said they weren’t completely adorable. And twin births occur in greater frequency among mothers giving birth using in vitro fertilization (IVF). In fact, according to the CDC (Centers for Disease Control and Prevention), twin births have increased two-fold over the last 40 years in the United States, due in large part to assisted reproductive technology.

The reason IVF results in more multiple pregnancies boils down to fertility doctors and their patients being able to place more than one embryo into the uterus during the embryo transfer phase of the IVF cycle. Placing two or more embryos in the womb considerably increases the odds of a multiple pregnancy.

The decidedly less adorable side of multiple births is the danger they pose to both the mother and the babies. Multiple-birth pregnancies carry an increased risk for a number of serious conditions and unfavorable outcomes including high blood pressure during pregnancy (preeclampsia), gestational diabetes, C-section delivery, preterm delivery, low birth weight, cerebral palsy, and stillbirth.

In light of this, it is our job as reproductive endocrinologists to educate our patients on the risks of a multiple pregnancy as they make important decisions relating to their IVF cycle.

Before advances in infertility science began leading to better success with transferring one embryo, it made total sense to transfer multiple embryos at once. The chance for successful implantation was relatively low, so doctors wanted to hedge their bets, even if it meant that their patient might give birth to multiples.

Since the early days, IVF technology and techniques have improved substantially, including much better vitrification (egg and embryo freezing) success. And with the advent and spread of preimplantation genetic testing, we can identify healthy embryos in the lab that are free from the genetic flaws that result in many pregnancy failures, IVF or natural.

Turning the ship around

Today, the need to transfer multiple embryos to increase the odds of pregnancy has diminished substantially, and so too has the need to expose mothers and babies to the risks of a multiple pregnancy. We’re far better equipped to identify one quality embryo in the lab. When a cycle produces multiple healthy embryos, we are able to safely freeze the ones that aren’t transferred for later use should the first transfer fail.

In cases where it is appropriate, we advocate for elective single embryo transfer (eSET), whereby a woman and her doctor make the decision to transfer just one embryo even when two or more healthy embryos are available.

Scientific consensus continues to point toward transferring a single embryo during IVF whenever possible. In their latest publication on the topic, a special embryo transfer committee formed by The American Society for Reproductive Medicine (ASRM) stated, “In patients of any age, transfer of a euploid embryo [one with normal chromosomal pairs] had the most favorable prognosis and should be limited to 1.”

As is often the case in medicine, what’s happening within clinics is lagging behind that which is optimal and recommended in light of the best available evidence. An article published last year in Fertility Research and Practice notes:

“A number of factors are thought to impede the widespread uptake of eSET in the United States, including a perceived lower overall success rate when compared with double embryo transfer (DET); lack of patient education regarding the risks associated with multiples and high dropout rate following failed cycles due to financial, emotional, and/or physical burden.”

You can see that much of the failure to adopt eSET comes down to a lack of education and understanding among IVF patients. Indeed, transferring two embryos at one time has the same success rate as transferring one embryo and then another frozen embryo subsequently if the first one fails. And the latter scenario carries substantially lower risk for a dangerous multiple pregnancy.

WIFC prioritizes single embryo transfer

The latest available national data from the CDC show that 28.5 percent of women under 35 chose eSET in 2014. These were women using their own eggs for fresh (unfrozen) embryo transfer.

While not a direct comparison, our current -house data from 2016 through this year show that just over 38 percent of all women treated at the Fertility Center who had more in than one healthy embryo available chose eSET. This is an encouraging trend, and we hope to see that number continue to rise in the years to come.

Women & Infants Fertility Center providers are part of the Warren Alpert Medical School of Brown University, and many are actively involved in clinical research. As such, we are wholly committed to examining the best and latest evidence and treatment recommendations to ensure that our patients have the best possible outcomes.