Quote Originally Posted by quickdodge®
The night before the baby was taken to the hospital, Arnold and the child's father went out for a short time and left Paris with a baby sitter, Rion said.

The mother didn't sense anything out of the ordinary until the next morning, when the child was found unconscious, Rion said.
Well, this is pretty easily solved.

The babysitter killed the baby. When the parents found the baby unconscious the next morning, the body was cold. They threw the baby in the microwave in an attempt to warm the baby back up and thus, bring it back to life.

Wow, I should be a detective.