Any tips for spotting a pregnant rat?

I’ve got a very small rat breeding project I’ve recently started up. I’ve had 1.2 rats (now 10 weeks old) in a tub for a month now and so far no babies. I’m not sure if either of the females are pregnant or not, I don’t know what to look for.
Are there any signs or ways to know if one of them is expecting or should I just keep waiting?

Backround: Rats have an unlimited supply of water and Harlan 18% protein lab block overhead and are kept at a consistent 75-77 degrees

When she looks like she swallowed a golf ball, you know shes pregnant :)

Are you seeing any sexual activity?
How old are they? 10wks?

they are still young, give em time.

one word

pear-shaped

Ten weeks is way too young to start breeding a female. If you've had them in together for any amount of time, they are most likely pregnant though. I would split the male from them asap. Most females that are bred so young are horrible mothers, they don't have many pups and most do not survive.

As far as being able to tell if they are pregnant, in the last week of pregnancy, there is no missing it. I have a few females that I've sent into rotation. As soon as they become noticeably pregnant, I will take pictures. :)

As many above have said you will know without question that you've got a pregnant rat on your hands.. Ilovelace said it will look like she swallowed a golfball, I say more like a Baseball!! LOL!

pear-shaped sums it up for me also the belly will feel firm

Hold them up so they stand tip toed, even in the beginning of pregnancy you can see that her abdomen will slightly curve outward. You should be able to feel soft yet solid pee to marble sized masses too. Take note of behavior, my does go from flicking their ears and bouncing off walls to cranky solitary hermits. Mine can manage to sit still longer during pregnancy.