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IVF and Elective Single Embryo Transfer
Elective single embryo transfer (eSET) is a growing trend for IVF patients. Doctors transfer one embryo and cryopreserve, or freeze, additional embryos for transfer in a frozen cycle. Why is this gaining popularity? Over the years, one of the concerns related to fertility treatment has been the rates of multiple pregnancy. Women who carry and deliver twins, triplets, or more are at greater risk for a number of conditions during their pregnancy such as preeclampsia and gestational diabetes. And twins are five times more likely to be premature than singletons. With that comes an increased chance of Cerebral Palsy, lung issues, ADHD, and even lower IQ in mid-childhood.
A recent study by Emory University School of Medicine and the CDC reviewed IVF cycles from 1999-2010, to look at trends in single embryo transfer and to identify factors that contributed to a “good perinatal outcome,” defined as a full-term pregnancy and the birth of a singleton baby with normal birth weight.
The researchers looked at more than 17,000 non-donor elective single embryo transfer (eSET) cycles. They found that eSET has increased steadily: in 2004, less than 1 percent of all fresh IVF cycles used elective single embryo transfer compared to 5.6 percent of cycles in 2010.
Compared with other embryo transfers:
- eSETs were nearly twice as likely to result in a good perinatal outcome
- 40.2 % of women under age 35 using eSET had a good perinatal outcome
- 32.5% of women age 35-37 using eSET had a good perinatal outcome
The researchers concluded, “Given the frequency of good perinatal outcomes among women aged 35–37 years, guidelines for elective single embryo transfer could be expanded to include patients in this age group with favorable prognoses.”
The American Society of Reproductive Medicine (ASRM) has published a set of guidelines on how many embryos to transfer in an IVF cycle, related to the woman’s age and prognosis:
- Women under age 35 with a favorable diagnosis – one embryo
- Women age 35- 37 – two embryos
- Women age 38-40 – two embryos
- Women age 41-22 – three embryos
According to Dr. Jenna McCarthy, a reproductive endocrinologist with South Florida Institute for Reproductive Medicine in Jupiter, FL, all fertility practices follow these guidelines but there can be a bit of a gray zone. For example, “A women age 35 with a favorable prognosis doing her first IVF and a 35 year old with three failed IVF cycles would have different recommendations,” she says. “For women in the 35 to 37 age range with good ovarian reserve and good quality embryos, single embryo transfer may be more appropriate.” It also depends on whether she has cleavage stage (day 3) or blastocyst stage (day 5) embryos, and the embryo quality, she adds.
The study and Dr. McCarthy both use the term “favorable prognosis.” She explains that this takes into consideration the number of previous IVF cycles, the underlying cause of infertility, ovarian reserve and sperm parameters.
“With my patients, at the initial consultation, I explain to them that a singleton pregnancy is much safer and healthier for the mother and the baby." But she also recognizes that most patients pay out of pocket and would like the fastest route to pregnancy.
What patients need to think about is whether they simply want a pregnancy or a healthy baby, McCarthy says. As a physician, she has to take into account patient desire and the “mistaken belief that twins are desirable.”
“If a patient has at least one additional good quality embryo to freeze in addition to transfer, the pregnancy rate is very similar” to the pregnancy rate of transferring two fresh embryos, McCarthy says. “Patients and insurance companies have to understand that single embryo transfer is a win-win.”