My dog had puppies yesterday, can I shower her today?

What is the need for bathing her?
If it isn't totally necessary I'd personally wait about a week, especially if she is a new mother, so she doesn't feel you are trying to take her away from her puppies.

If she is messing around her rear (which is why I'm assuming you want to shower her) Just get a tub of warm water and a cloth and wash just that area while she is still in the room with the puppies.
Make sure you dry her thoroughly so she doesn't transfer the moisture to the pups and they don't chill.

Is there any other help you need with your new puppies?
They can be quite demanding and hard to look after.

If you do see a need to bathe the dog, use Aveeno baby soap. It has no dyes, no scent and is easy on the skin. Don't wash her bag either... it may taste bad and the puppies might not want to nurse, and the first week is the most critical for the puppies to get nutrients into their bodies.

Last year I had a female welped 12 puppies, she was pretty icky. We did a quick rinse with her when she left her puppies to go potty. Don't take her away from her puppies unwillingly. There is a good chance she could bite, or you could have a very miserable time washing her. If she wants to get up and go potty and maybe eat while away from her pups, then I wouldn't see any harm in cleaning her up a bit.