Pet owners must take many things into consideration in their quest to keep animals healthy and happy. One of those considerations involves animal reproductive health.

Veterinarians as well as animal welfare organizations urge pet owners to spay or neuter their pets, not only to provide various health benefits, but to help reduce overpopulation in pet communities.

Cat pet parents must be especially diligent in their quest to squelch reproduction to help control cat populations. According to The Spruce: Pets, female cats that are not spayed will come into estrus (heat) as early as age four months. The animal health resource BondVet says a cat can go into heat as often as every two to three weeks. Generally, though, cats are seasonal breeders, indicates the United Kingdom-based RSPCA, which means heat cycles slow down in autumn. Another thing to note is that cats do not enter menopause like people and other animals. That means a female cat can continue to reproduce well into her senior years.

Cats can become pregnant even during the first estrus cycle. A feline’s pregnancy lasts around 63 to 65 days, or about nine weeks. A cat also can be impregnated again very quickly after giving birth, as nursing kittens will not prevent a subsequent pregnancy. The average litter size is three to six kittens, so it’s easy to see just how many kittens can be born of one cat if she’s left to her own reproductive devices. Females also can be mated by more than one male or even one of their male relatives.

While there is still some debate among veterinarians as to the best age at which to spay or neuter cats, the general consensus seems to be the earlier the better, particularly if cats have access to other cats that are not fixed. This can occur as early as age six to eight weeks, while standard spays and neuters occur at five to six months of age. Vets who advocate for spaying before the first heat say it nearly eliminates the risk of mammary cancer, and spayed cats will not develop ovarian and uterine cancers, according to PetMD.

Physiologically and behaviorally, cats are built to reproduce as frequently as possible. Pet owners must put a stop to that to protect against overpopulation and to reduce unwanted behaviors like inappropriate marking, aggression and other issues.