It doesn't happen often, but surgeons sometimes can reach into the womb to repair a birth defect. The Mayo Clinic recently performed one such operation on a fetus with spina bifida, an opening in the spinal cord that can cause disability and paralysis.

The baby girl was born July 16 and is developing normally, Mayo says.

In announcing the operation (a first at Mayo), the clinic released a cool animation of how it works. Don't worry, it's sanitized and easy to watch.