They don't entirely know the severity of the disorder. The kid could live an just be fragile, or the kid could die. If it's going to die shortly after birth, then if I were in their shoes I would want to carry to term so I could hold my baby during it's very brief life. If it will live then... it'll live. A person with type 3 ostiogenesis imperfecta can live a perfectly happy life, though surgery is never fun. One of my best friends has type 1 and has "obliterated" (doctor's words) a few bones but he's worth keeping around. My cousins have ectodermal dysplasia, which means lots of surgeries, but they're worth keeping around. They're all happy, disorders and all, and we're happy with them around. Don't gotta go aborting every little thing.