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When it comes to in vitro fertilization, the message of a new study is simple: Less is more.

In the past, doctors practicing IVF often transferred multiple embryos to a woman’s body at once, in the hope that at least one of them would lead to a successful pregnancy, according to a report by Reuters Health.

But in a new study, researchers at the University of Iowa in Iowa City found that women who had only one embryo transferred during IVF didn’t have lower chances of getting pregnant, but they did have a lower risk of giving birth to twins than women who had multiple embryos transferred.

Twins, triplets  or other multiple-set children are not necessarily undesirable, but according to the American Society for Reproductive Medicine, multiple births increase the likelihood that mothers and babies will have health problems, such as diabetes, during pregnancy, premature births and preeclampsia.

The study’s author, Jessica Kresowik, told Reuters Health that her fertility clinic instituted a single-embryo policy in 2004 for women age 38 and younger getting their first IVF and who had a good chance of getting pregnant.

When she and her colleagues studied the numbers of live births before and after the policy, they found that the use of single embryos were just as effective at leading to live births, and maybe even more effective – 51 percent of patients gave birth to live babies before the policy, and 56 percent did after the change to single embryos.

The proportion of women with multiple births dropped from 35 percent to 18 percent.

IVF specialists have been favoring the transfer of fewer embryos in the past few years, citing concerns about the health of mothers and babies.  

Dr. Bradley Miller, who specializes in IVF at the Reproductive Medicine Associates of Michigan in Troy, Mich., said he believes policies like the one at Kresowik’s clinic are the way of the future.

“Complications from premature births can be lifelong medical issues or the babies simply don’t survive,” Miller said. “In the long term, these single-embryo practices are going to provide for healthier babies and obviously decrease rate of multiples across the nation.”

However, Miller said many patients often request multiple embryo transfers, despite knowing the risks.

“They want to have a better chance of pregnancy and they’re not necessarily opposed to having twins,” Miller said. “The crucial part of single-embryo policies is educating the patient that having twins isn’t necessarily going to have a good outcome every time.”