Do you have an "innie" or an "outie?" People sometimes ask themselves this question while contemplating their navels. So what's a navel anyway? The medical term is umbilicus, and almost all mammals have one because they are live-bearers as opposed to egg-layers -- the duck-billed platypus is a strange hybrid sort of mammal that lays eggs. Since live-bearers must nourish their young in the womb, they have belly buttons, because it is the remnant of the umbilical cord, the lifeline between mother and fetus.
The gestation period for kittens is around 65 days. During this time, the kittens are developing inside the mother's womb. If the mother cat, called a queen, has a home and is well fed, her kittens will be nourished through her diet. If the cat is a stray, and her meals are few and far between, or if she eats food with no nutrients, or tainted with parasites or bacteria, her kittens will suffer the consequences. There won't be enough nourishment and they will be born sickly and weak. The kittens are fed inside the womb not by eating with their mouths, but by absorbing all they need through their bloodstream.
When humans are pregnant with identical twins or triplets, they share a placenta. If fraternal twins, they develop their own placentas. With felines, each kitten has his own placenta and umbilical cord. The umbilical cord is attached to the mother, and oxygen, vitamins, minerals and immune-boosters are dispersed to the kittens through this route so they can grow strong. If the mother is well-fed, the kittens are well-fed too. If the mother eats anything toxic, that substance will pose a threat to the kittens.
All in Proportion
The kittens grow over the 65 days they are developing in the womb and the size of the fetus depends on the size of the litter and the quality of the food. If the kitten is the only fetus, or is just one of two, the kittens will grow larger since there's more room for them to grow. This is especially true if the nourishment they're getting through the umbilical cord is high in calories and fat content. When the kittens are born, the mother severs the umbilical cord by chewing through it, leaving a tiny scar that disappears as the kitten grows. It's very unusual to be able to see a belly button on an adult, non-human animal.
Caring for the Queen
When a cat becomes pregnant, either by accidental or deliberate breeding, it's important to keep her on a steady diet of high-caloric, vitamin-packed food. In the early stages, don't make any changes to her regular diet. After two weeks, add some protein such as fish or cooked chicken. In the later stages, switch the mom to kitten food as it is rich in fat, calcium and everything a kitten needs to grow strong. The stress of the pregnancy and the sharing of nourishment with the kittens can cause the mother's immune system to suffer, so adding additional quality food will help boost her own resources and keep her strong. Keeping stress to a minimum is important too, as stress can affect cats just as it does humans; it wreaks havoc with the body, putting both the mother and the kittens at risk.