You can bathe a pregnant dog, but you need to be very watchful of the pressure placed on the abdomen. You should bathe her at least once a week, depending on the breed of dog you own. Your pregnant dog needs grooming just as much as any other dog. Learn more about the precautions you should take when bathing her at http://www.ehow.com/how_2352523_bathe-pregnant-dog.html.
It depends how long has she been pregnant when a dog is preganated it takes 63 days till there birth so 45 and up i wouldnt because giving her a bath can stress her and cause her to have puppies early and there not going to be fully developed Less that 45 days give bath but barely any pressure on the stomach or you can kill her pupies.