Medical groups representing U.S. fertility experts, alarmed by rising numbers of multiple births, on Tuesday advised limiting the number of embryos implanted in women undergoing in-vitro fertilization.
The latest medical evidence “clearly indicates” that high pregnancy rates can be achieved even with fewer embryo transfers, Dr. Marc Fritz, chair of the American Society for Reproductive Medicine’s practice committee, said in a statement.
Some patients and clinics have opted for transferring several embryos during a single cycle in order to increase the odds of success but pregnancies involving two or more fetuses are at risk of complications including premature delivery, which increases a baby’s odds of suffering medical and developmental problems.
The new recommendations to fertility specialists, which are not enforceable, call for transfer of no more than two embryos for women under age 35, and say the transfer of a single embryo should be considered.
For women aged 35 to 37, no more than two later-stage or three earlier-stage embryos should be transferred, according to the new guidelines.
The recommendation rises to as many as four embryos for patients aged 38 to 40 and to five embryos for women over the ago of 40.
More than a third of pregnancies conceived using assisted reproductive therapies result in a multiple birth, which has helped to drive up the rate of U.S. babies born prematurely each year to 12.5 percent, according to the March of Dimes.
“New parents may think there’s more to love when you have more than one baby but there’s also more to worry about; more than half of twins and nearly all triplets are born prematurely, associated with an increased risk of death and disability,” Dr. Nancy Green, March of Dimes medical director, said in a statement.