Ruling on female circumcision

Is female circumcision sunnah or a bad practice? I read in a magazine that female circumcision in any form is a bad practice that is harmful from a medical point of view, and that it may sometimes lead to sterility. Is this correct?

Praise be to Allah, and blessings and peace be upon the Messenger of Allah:

Circumcising females is sunnah; it is neither a bad practice or harmful, if it is done within moderation. When extreme forms of female circumcision are carried out, harm may result.