Here is a link for info, and a paragraph.
http://www.hdw-inc.com/spayneuter.htm
Most frequently, it is recommended that female kittens be spayed at six months of age, or preferably before their first heat. The surgery, called "ovariohysterectomy", involves anesthetizing the animal, and the veterinarian makes an incision through which the cat's ovaries and uterus are removed. The surgical incision is then closed by either non-absorbable stitches (which must then be removed in approximately 7 to 10 days); or by sub-cuticular stitches, or by sutures that are placed below the skin and that gradually dissolve on their own in the body. There is another procedure that can be performed on female cats, and that is called a "tubal ligation", which is the surgical procedure which makes the female sterile, but does not prevent her from coming into heat and attracting males. Obviously, tubal ligation is not very popular for that very reason!!