Transferring fewer embryos in appropriate clinical conditions reduces the rate of multiple gestations without impacting live birth rates, according to new recommendations from the American Society for Reproductive Medicine and the Society for Assisted Reproductive Technology.
The recommendations are the first update since 2013.
Dr. Penzias and fellow committee members reviewed national data from 2013 that showed similar pregnancy rates for women aged 42 years and younger who received a single euploid blastocyst or two untested blastocysts. But the risk of twins was significantly reduced with single embryo transfers ().
The recommendations state that euploid embryo transfer should be limited to one for women of any age with a favorable prognosis, and for women younger than 35 years regardless of the embryo stage.
Patients aged 35-37 years should first consider single-embryo transfer, and patients aged 38-40 years should receive single-blastocyst embryo transfers if euploid embryos are available, but no more than three cleavage-stage embryos or two blastocysts.
Patients aged 41-42 years should receive single blastocyst transfer if euploid embryos are available, or no more than four cleavage-stage embryos or three blastocysts.
For patients in each age group without a favorable prognosis, the recommendations support transfer of an additional embryo based on individual circumstances and with the condition of patient counseling about the risk of multiples. Additional embryo transfers also may be considered for women who fail to conceive after multiple cycles.
However, “patients with a coexisting medical condition for which a multiple pregnancy may increase the risk of significant morbidity should not have more than one embryo transferred,” the committee members wrote.
The recommendations also call for single-embryo transfer in donor cases where the oocyte donor is younger than 35 years. For patients using frozen embryos, transfers should not exceed the recommended numbers for each age group, and decisions should be based in part on the patient’s age when the embryos were frozen.
The new recommendations will impact clinical practice by providing clinicians with the data they need when counseling patients, said Dr. Penzias, a reproductive endocrinologist in Waltham, Mass., and a clinical professor at Harvard Medical School.
Patients should receive the take-home message that “placing more embryos at once isn’t the best way to achieve their goals,” he said. The recommendations “will help to continue the trend toward single-embryo transfer in an ever-widening group of patients,” he noted.
Looking ahead to research that might inform future recommendations, Dr. Penzias noted, “noninvasive assessment of embryo potential is actively being pursued. [Plus], better understanding of the endometrium and issues around implantation,” he said.
The committee members who developed the recommendations reported having no relevant financial conflicts.