This toddler is the first to have been treated for her disease before she was born

According to her parents, Ayla Bashir is “a miracle.” The talkative and smiley 15-month-old is also a pioneer—the first person to start receiving medical treatment for her genetic disorder before even being born.

Ayla is the first participant in a clinical trial that will test medical therapies for 10 fetuses with genetic diseases. The idea is that by starting treatment earlier, doctors might have a better chance of providing the eventual children with a better quality of life.

But clinical trials on fetuses raise plenty of ethical questions. How should we be testing treatments on vulnerable fetuses that can’t give consent? And what does this mean for the pregnant person?

Before Ayla was conceived, her parents had already lost two daughters to Pompe disease—a rare genetic disorder that can affect the heart and muscles. Zara died at the age of two, and Sara passed when she was only six months old.

“For this pregnancy, [the parents] were definitely motivated to try to do something different,” says Tippi MacKenzie, a pediatric and fetal surgeon at the University of California, San Francisco...