A World Health Organization official says having doctors supervise genital cutting is "the same as attempting murder with a clean knife."
A report from the WHO says the practice is torture and must be stopped, even if it's done by medical workers. It's mainly done in Africa and the Middle East.
An assistant director-general of the international health group says the practice "is the worst thing that a medical doctor could possibly do."
A UNICEF report last year said more girls are being cut by medical workers, which may help prevent the spread of HIV through the use of cleaner instruments. But the WHO opposes anything that might legitimize the practice.
Those who practice it believe the cutting tames sexual desire and increases a girl's marriage chances.
The WHO study in The Lancet medical journal found the practice inflates risks of complications for both mother and child in birth.