New Single-Embryo Transfer Practice Successful

Megan Brooks

November 27, 2019

PHILADELPHIA — Revised single-embryo transfer guidelines have led to fewer twin births in the United States, with no decline in the live birth rate, report investigators.

The guidelines — revised in April 2017 by the American Society for Reproductive Medicine (ASRM) and the Society for Assisted Reproductive Technology (SART) — recommend that two embryos be transferred only after the failure of multiple embryo-transfer cycles in women younger than 38 years with a good prognosis.

The previous iteration of the guidelines allowed the transfer of two embryos to patients in this category after the failure of only one single-embryo transfer cycle.

"Twin pregnancies come with a lot of complications and other issues, much more so than singleton pregnancies," said Allison Eubanks, MD, from the Walter Reed National Military Medical Center in Bethesda, Maryland.

"The conclusion of our study is that women younger than 38 years who have just failed one transfer should get a single-embryo transfer in the next cycle. After that, it should be shared decision-making," she explained here at the ASRM 2019 Scientific Congress.

Walter Reed adopted the 2017 guidelines immediately after their release, "with no exceptions," making it an ideal dataset to analyze their impact, Eubanks explained.

In their retrospective study, she and her colleagues compared assisted reproductive technology outcomes in women younger than 38 years in the 2 years before and the 2 years after the revised guidelines were adopted. The women in the study cohort were on their second embryo transfer cycle, using their own eggs, and had not undergone preimplantation genetic testing.

During the 4-year study period, there were 367 live births.

The data show significant reductions in the number of embryos transferred, the rate of twin pregnancy, and the rate of twin live births after the revised guidelines were adopted, but no overall reduction in live births.

Table. Outcomes Before and After the Revised Guidelines
Outcome Before Revision After Revision P Value
Average embryos transferred 1.4 1.0 .001
Clinical twin pregnancy rate 14.2% 2.5% <.001
Twin live birth rate 12.5% 2.5% <.001
Overall live birth rate 46.9% 50.3% .31

The percentage of transfers with good embryo quality increased from 61% to 67% during the study period. The live birth rate was similar before and after the revision, even after adjustment for embryo quality (P = .52).

"National SART data are also consistent with the Walter Reed data," Eubanks told Medscape Medical News.

This study shows that single-embryo transfer "works very well in this age range," said ASRM Past President Christos Coutifaris, MD, PhD, from Penn Medicine in Philadelphia.

"Despite some patients' wish to have twins, we must advise them that SET is safer and therefore more practical," he added.

"Not Every Rule Applies to Every Patient"

It's important to note that most of the single-embryo transfers today are done at the blastocyst stage, "when the embryo has already declared itself as being a better-quality embryo because it has continued to the blastocyst stage on day 5," said Zev Rosenwaks, MD, director of the Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine at Weill Cornell Medicine in New York City.

However, single-embryo transfers apply only to young women who are first-time patients, not those who have failed multiple IVF cycles with single-embryo transfer, said Rosenwaks, who was not involved in the study.

"Occasionally, we do put more than one embryo in a young woman, but there are specific reasons for doing so. Obviously, all of the criteria must be looked at with the knowledge that medicine still should be practiced individually for a given patient, because not every rule applies to every patient," he told Medscape Medical News.

American Society for Reproductive Medicine (ASRM) 2019 Scientific Congress: Abstract P-99.

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