A few weeks after the kittens are born she'll go into heat. Quite an annoying sound at times. Some kittens will feel the need to feed off the mother even when they are 10 weeks old but thats when you have to put your foot down and stop them. If you have an unwanted pregnancy you can get her spade while she is pregnant which is the same as an abortion but in some cases if you do not allow your female to breed at least once in her life time then she could become aggressive and resent you for it. I know two cats that have turned that way.
Cats can come into heat while nursing. Do not allow your cat access to unneutered male cats while nursing or she may become pregnant again. The nursing period lasts until the kittens are 6-8 weeks of age. After the kittens are weaned you can have your cat spayed if you want to prevent further litters. Cats can be very prolific breeders.
When the baby's are weened she'll go back into heat.
I have had them to come into heat again around eight weeks after the kittens were born.
My cat fell pregnant as soon as she had her 1st litter so anywhere between 1-8wks after pregnancy