A few key data points about Amelia Sloan: She likes to suck her own toes. She wears pink tutus. She doesn’t do interviews with journalists. She was born in Falls Church, Va. on April 25, 2013, at 6:54 p.m., weighing in at 8 pounds, 2 ounces. Amelia entered the world right on schedule, but not all her fellow Tauruses did, a fact that raises other key data points: In the United States, some 500,000 babies are born prematurely every year. At birth, each weighs less than a two-liter soda bottle. They cost the healthcare system an estimated annual $26 billion. More than 330,000 of them don’t survive the first year, and many of the rest suffer life-long health and cognitive problems. And doctors don’t know why.