heat during pregnancy?

We have adopted a pregnant stray cat. Her abdomen is quite distended and she eats a lot, so we assume that she is close to delivery. A few days ago, she started displaying all the symptoms of heat. We thought this would not happen during pregnancy. Is it normal? Any suggestions? Thank you.

My guess is her kittens will be arriving soon. They display similiar traits right before their kittens are due to arrive as they do when they are in heat. Look for her to start pacing and provide her with a good deep birthing box in a secluded and dark (and warm place)