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While spaying is traditionally recommended for kitties between 4 and 6 months of age, spaying as young as 8 weeks old is considered safe, according to Cat Channel. Many animal shelters actually spay kitties prior to adopting them out at this age.
Both male and female kittens can be spayed as early as 12 weeks of age, although this depends on the vet; many will now advocate early spaying whereas as others will prefer doing the procedure when the kitten is near four or five months old.