American Shorthair female cats can give birth when they are 1-5 years old, with 2-4 years old being the best reproductive stage. American Shorthair female cats will go into heat for the first time when they are 8-10 months old. Breeders should not mate the cats when they are not fully mature at this time. They can only mate after they grow to 1 year old and develop again. Female cats may not cooperate when mating for the first time, so they can be paired with an experienced male cat.