It will give you a good idea, but like Mardelin said, there is always the possibility that one is hiding in there. It will also give you a heads up if the pups look too big to deliver and there is a high possibility that the bitch will need a c-sectioned. IMO, being able to plan with you vet a section ahead of time is better than having to take a dog in distress to an after hours office.
Wishing you and your girl a healthy and safe delivery!
