A major health insurer won't pay for botched surgeries.

Starting next year, Wellpoint will no longer pay for certain medical mistakes, like surgery on the wrong patient or body part, or a mismatched blood transfusion.

The company's 35 million customers won't have to foot the bill either, even if another surgery is needed to correct the problem.

Wellpoint is working its new policy into hospital contracts.

It's hard to track how many major medical mistakes occur every year, and a few states now require hospitals to report them.