Doctors say they’ve helped an infertile woman become pregnant by combining her egg with that of a donor—another successful use of a controversial IVF technique.

The patient: She’s a Greek woman of 32, and four previous IVF attempts didn’t result in a pregnancy. To help her, doctors moved the DNA from one of her eggs into the egg of a donor and then fertilized it.

She’s now 27 weeks pregnant, according to Nuno Costa-Borges, cofounder of Embryotools, a company in Barcelona, which collaborated with IVF doctors at the Institute of Life in Athens.

The technology: It’s like egg donation—and it requires donated eggs—except the baby is related to the mother. That could be a very big deal for helping younger women with infertility.

“There are disorders that cause young women to need egg donation, but it’s very traumatic for them,” says Costa-Borges.

Is this more three-parent babies? Yes, it’s often called that. That’s because the donor egg lends the baby its mitochondria, energy-making structures that have their own genetic material. That means a tiny fraction of the embryo's DNA comes from the donor—hence "three-parent babies." But don’t call it that, pleads Costa-Borges. The scientific name for the technique is “spindle transfer,” a reference to the chromosomes of the mother-to-be. It has been used in the past to make sure children aren’t born with fatal genetic diseases passed down from their mother. This latest pregnancy is a little more unusual as it was used to treat infertility.

Banned in the US: The technology was first developed in the US by the Oregon laboratory of Shoukhrat Mitalipov, who tested it in animals. But in 2015 the US Congress banned its application in America.

That’s why it is all taking place overseas. The first birth of a baby from the spindle transfer technique was announced in 2016 by an American team that worked in Mexico. Since then, a clinic in Ukraine has produced a few children via a related technique. The American doctor offering the service, John Zhang, was later warned to stop advertising it by the US Food and Drug Administration.

What’s the controversy about? A lot of people are just morally opposed to anything strange and new—particularly around birth and pregnancy. Ethicists at Oxford University have written up the new case and list the many objections that have been raised in recent years. It’s also hard to prove for sure whether a new way of making people is really safe, although Embryotools says it has spent several years trying the technique on animals like mice.