I have two indoor cats who're sisters. One of them got pregnant and had kittens, and the sister did not go in heat once during the 3 months we had the kittens. Do kittens prevent a cat from going in to heat? If so, how?
- Sister went in heat the same time mamma did and although she mated she didn't get pregnant, this will cause the cat to enter a pseudopregnancy state, the cat will think it's pregnant and won't go into heat for another several months.
- Sister might have a hormonal(ovaries) problem/defect, I can't elaborate much on this, but one of my cats had ovaries with defects(low hormone production) which would cause her to only go into heat one or two(pushing it) times a year, also if you're really worried, I'd take her to the vet since it could be tumors in the ovaries as well(worst case)
- If she didn't go in heat when mamma did(or at all), don't worry... Some cats just bloom later than others. It's called an average for a reason, there's no rule as to when a cat should start going into heat, only approximations.
In humans, the mother will usually not begin to be fertile until the body fat ratio returns to a region where the new fetus can be amply supplied for growth. A breast feeding mother will usually remain comfortably below that threshold, so there is a general barring of a new child until the old is out and about.
As mammals, mother cats probably have a similar mechanism to avoid overlapping litters.