Meeting the doctor ahead of time can give you an opportunity to talk to them and find out if they have any particular rules for photographing or recording labor and birth.
It also gives you a chance to talk to them about what happens if your client has a cesarean. Some doctors will arrange it with the anesthesiologist to get the photographer back into the OR in non-emergency cases. (In an emergency, you will not be allowed back there.). In most cases the anesthesiologist has the final say because you would be in their area to shoot. Don’t take it personally if they say no to a photographer in the OR. They are looking out for your client.
Birth Photography can be a risky business. But it has to be one of the holy grail's of photography. Black and white would be the registered filter to use and no flash, what so ever. This will involve a lot of unplanned events that could take place and it would be better to talk to the nurses and doctors before hand.