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Yes, the first puppy will be preceded by a water bag. If she happens to be sitting as it is passed you may not see the bag, only a spreading puddle. It could appear from the vulva like a balloon if she's standing. The first puppy should follow the expulsion of the water bag within four hours. More likely, you can expect the first born within a half-hour. I'm including a few links about whelping which you can read & therefore know more of what to expect during whelping. Please let me know if you should have any additional questions.
Whelping Puppies, Breeding Dogs
Pregnant dog - pregnancy signs in dogs - Article on Pets.ca