Cats have several periods of heat over the course of a year. A heat period lasts between 4 to 7 days if the female is bred, if she is not bred the heat period can last longer.
After mating, the female will give herself a thorough wash. If a male attempts to breed with her at this point, the female is likely to attack him. Once the female is done grooming the cycle will repeat.
The male cat's penis has spines which point backwards. Upon withdrawal of the penis from the vagina, the spines rake the walls of the female's vagina, which may cause ovulation. Ovulaton does not always occur and females are rarely impregnated by the first male that they mate with. Female cats may mate with more than one male when she is in heat, meaning different kittens in the same litter may have different fathers.
The gestation period for cats is approximately 63–65 days. The average size of a litter is three to five kittens, the first litter usually smaller than subsequent litters. Kittens are weaned between six and seven weeks, and cats normally reach sexual maturity at 4–10 months (females) and to 5–7 months (males).
Cats are ready to go to new homes at about 12-13 weeks old (the recommended minimum age by Federation Internationale Feline), or when they are ready to leave their mother. Cats can be surgically sterilised (spayed or castrated) as early as 6–8 weeks to limit unwanted reproduction.