A toddler is thriving after doctors in the U.S. and Canada used a novel technique to treat her before she was born for a rare genetic disease that caused the deaths of two of her sisters.

Ayla Bashir, a 16-month-old from Ottawa, Ontario, is the first child treated as a fetus for Pompe disease, an inherited and often fatal disorder in which the body fails to make some or all of a crucial protein.