Momma Cat's back?

The mother of Josie and Huggy Bear appeared to be pregnant last time we saw her. The temperatures outside dropped and our neighbor took her in, I assumed. After a while, the weather had warmed up but we still didn't see Momma Cat so I thought maybe they found her a good home. But we saw her out back eating grass the other day. I couldn't tell if she had had babies or not, but there were no kittens prancing around with her.