When my cat had kitten I would not let her out side until the kittens where around 2 weeks old.
My cat has had a few litters she goes out shortly after she has had them but always wants right back in. As long as you have a way to let her in and out easy she can go out whenever she wants.
Anytime because some cats feel like hunters and they try to be good moms by catching field mice and bringing home " the prize " to her family.
Yeah, this post was three months ago and, if this person listened to the rest of these replies, this cat should be delivering her next litter of kittens any day. This is why approximately 10 million domestic pets in shelters are killed each year. People who REALLY love animals do the responsible thing and get their pets spayed and neutered. Think differently? Why don't you go volunteer at a local shelter? You get to know the animals. You even get attached to some. The next week you go in and there's an entirely new group, because the ones you got to know are all dead!