If the owner of the stud you are using is happy to let you go ahead before results are back then you should look for another stud dog. No reputable stud owner would agree to a mating without sight of the results of necessary health tests.
Depending on when she was hip scored if you ring your vet and explain she has come into season and you are wanting to mate her (possibly) sometimes they will ring the BVA and ask if they have been done yet.
Inconvenient as it may be there is really no rush to amte the bitch this particular season as she is oloy barely old enough for breeding anyway, for a large breed and in fact 3 years of age is a perfectly appropriate age for a first litter.