Domestic and feral cats that are not spayed or neutered can start mating and reproducing when they are between four and five months old. A female house cat can go into heat at four months.
Until she is spayed or becomes pregnant, a female cat repeats the estrus cycle periodically throughout the year, especially during spring, summer and early autumn.
When a female cat is in heat, she may go to great efforts to meet and mate with a tomcat. Signs that a female cat is in heat include increased affection, genital grooming and calling meows. Signs of pregnancy in a female house cat include rosy pink nipples, a vigorous appetite and abdominal swelling at around five weeks. The typical house cat gestation period is approximately 65 days.