With regular rats I pull the females when they look like they swallowed a baseball. I keep them separate or with another mother until their babies are ready to be weaned. Then they go back into the breeding rotation. I have had a lot of success doing it this way. When I clean each week I rotate my females through my males so the male sees a different group of females each week. I am pretty new to breeding ASFs but from everything I've read, they are much more sensitive to change so I am leaving my 1.2 or 1.3 groups together all the time.