Cats are prolific breeders. Females take just 6 to 9 months to reach sexual maturity; but it is not unheard of for female kittens as young as 4 months to become pregnant. Males mature a bit later but both sexes can breed before they are a year old. Although female can become pregnant at any time of the year, there are specific mating seasons when cats become sexually active. In northern Europe it is usual for domestic female cats to come into heat (estrus cycle) in January and then again in June. The estrus cycle is the period in the female reproduction cycle when mating is most likely to occur. A heat period lasts about 4 to 7 days if the cat is mated and longer otherwise. Female cats indicate their readiness to mate by calling for male company with a special type of yowl, which like the (highly vocal) mating itself has often disturbed the sleep of humans who live in the vicinity.
One of the most interesting features of the reproductive process of cats is a phenomenon known as induced ovulation. The male cat's penis has backward pointing spines which scratch the interior of its partner, and cause ovulation to occur. Because pregnancy will not take place without this stimulus, quite often the first cats to mate with a queen with not father any kittens. However, the super-fertility of cats means that once she gets started, the female is capable of having a number of partners, and bearing kittens from several fathers in the same litter. The mother's eggs are fertilized in the oviduct and arrive in the uterus 4-5 days after mating. Cats do not go about the process quietly, and to the unpracticed ear the process sounds remarkably like a prolonged and very vocal cat-fight.
Pregnancy lasts between 56 and 71 days, with the average pregnancy taking 68 days. Litters are most commonly of 3-6 kittens, but a single litter may have as many as nine. The record was a litter 19 kittens; the mother being a Burmese/Siamese cross from Oxford shire in