It is much healthier for a female to be spayed before her first heat cycle, it can prevent mammary and uterine cancers and infections. It also reduces the urge to escape outdoors where she could be hurt by cars or other predators.
While we all love our animals like our children, we have to remember that cats are not human. A cat or dog isn't going to feel sad, or feel something is "missing" not having a litter of kittens.
It can be dangerous not spaying a female. If a female continues going into heat cycles, it can cause many problems. Please spay her as soon as possible. There are already many cats/kittens needing homes because of people wanting "just one litter" or their unaltered female gets out of the house and accidently gets pregnant.
If you do want to experience a birth, please go to your nearest rescue or shelter and foster a pregnant mother. You will be helping out, more than you know.