If you're giving your female kitty a good looking over to detect any signs of pregnancy, don't use her nipples as a reliable confirmation. Just like in humans, queen cats have nipples whether or not they're pregnant. To drive the point home even further, male cats sport them, too!
Though cats always have nipples no matter what, pregnancy does indeed cause them to slightly change appearance. According to the University of Wisconsin at Madison's Department of Animal Sciences, feline gestation typically lasts for just over two months -- think 63 days or so. If you're looking for any differences in a cat's nipples during pregnancy, play close attention around her third week. At this time, you may notice that her nipples will start to take on a markedly "fuller" appearance. They might become significantly bigger and redder than usual, too.
As a cat's parturition date gets closer and closer, perhaps around her seventh week, you may observe that not only do her nipples appear much more prominent, they also may begin producing milk. Don't be alarmed if this doesn't occur at this point, however. Some queens' don't show signs of milk until the wee kittens are born.
Other Signs of Feline Gestation
The presence of nipples is certainly not an indication of feline gestation. However, that doesn't mean that it's always hard to tell whether or not a cat is indeed "with litter."
For example, if a cat's estrus cycles abruptly stop, then similarly to human menstruation, she very likely is pregnant. Also be on the lookout for signs including elevated appetite, unusually affectionate and cuddly behavior, nesting, vomiting and, unsurprisingly, a protruding belly.
If you're still uncertain about your little one's possible pregnancy, take her to the veterinarian for an examination to be safe.
If your queen isn't pregnant -- and you want to keep it that way -- consider getting her spayed. Not only will the surgical procedure spare her the discomfort and stress of her heat cycles, it will also prevent her from the bodily difficulties of pregnancy -- not bad. Feline overpopulation is also a troubling epidemic, so if you're a concerned member of your community, spaying may be the responsible and loving thing to do.