She has moved her kittens behind the sofa probably because its darker there and warmer and also she will feel safe there. If she is looking after her kittens well and not abandoning or leaving them for to long atall then they should be fine. Im not sure why she is meowing but someone on here should be able to help you. Or take her to the vet. My cat is pregnant and due this week
My girl did that when she had her baby. When she leaves him for a little bit she will periodically call out and until he meows back. It's a mama way of communicating, however I would check her out further. First things nurses do is assess the situation. Does any of her breasts look swollen and feel hot to touch? Is there anydischarge from her vaginal area? If the kittens healthy and eating properly (appear to be getting bigger)? Any one who has a new mom cat and newborn kittens needs to watch their cat closely. Cats could get an embolus from a piece of the placenta that travels to the lungs and kills them or they could get an infection in the breasts or uterus which is fairly common. Keep an eye on her if she continues to act oddly I would bring her in to the vet or at least call one to see what they want you to do.
My cat had kittens almost 3 years ago. A few weeks into the nursing she started moving them to new locations periodically. Which is all normal behavior. I hated the spots she chose though. I used to sleep on a coach bed and in the middle of the night she would move the kittens under the coach bed. I would have to move them back every morning so that I could fold the coach bed up.