Not necessarily. I breed rats for feeders, not pets, but I want to provide them with the best possible care and letting a mother wait until she has enough good size on her is important in my opinion. (just my opinion, nothing else)

We tend to frown upon someone wanting to breed their 800g female ball python. We warn against egg binding, small clutch size, etc. But as soon as someone has a lowly feeder/breeder rat, its ok to put her through the stress of pregnancy and raising a litter when she's small. Not saying others are wrong in breeding their rodents smaller/younger, I'm just wondering why it is okay to do so "just because they can".

I will wait until my girls hit 16weeks old. At that age I can make sure they have a good weight, and are overall healthy.

A note on breeding small females. I had one female. She was several months old. I had waited a long time to start breeding her because she just seemed so small. I wanted to get some more size on her. When I realized this was as big as she was going to get (probably around 180-200g or so), I went ahead and threw a male in with her. She got pregnant, had the litter, and died a day or two later from the stress.