Jennifer Cantor, a 34-year-old surgical nurse from Huntsville, Ala., loves being pregnant. Not having children, necessarily—she has one, an 8-year-old daughter named Dahlia, and has no plans for another—but just the experience of growing a human being beneath her heart. She was fascinated with the idea of it when she was a child, spending an entire two-week vacation, at the age of 11, with a pillow stuffed under her shirt. She's built perfectly for it: six feet tall, fit and slender but broad-hipped. Which is why she found herself two weeks ago in a birthing room in a hospital in Huntsville, swollen with two six-pound boys she had been carrying for eight months.