What do you call a place that pregnant cat sleeps?

There isn't a specific term for a place where a pregnant cat sleeps. You can simply say:

* Her nest

* Her sleeping spot

* Where she likes to sleep

* Her favorite spot

You could also use a more descriptive term based on the location, like:

* The box she's using as a den

* The blanket she's curled up in

* The sunny spot on the rug

The most important thing is to make sure the pregnant cat has a safe, comfortable, and quiet place to rest.