Nope. He'll try to ride her and may even hurt the calf. Estrogen levels increase during labour which can make the bull think she's going into heat instead of pushing out a calf, and instead will try to push himself in when she's trying to push out a calf. Not to mention the fact that the bull may try to head-butt or even trample the new baby calf because it's something new in his pasture and impeding his attempts at breeding the heifer. It'll make for a bit of a head ache, so you're better off separating the bull from the calving heifer.
Around here (in VA) I see bulls in the fields all the time with cows with newborn calves at their side. The bull is used as herd protection. I believe if it was a problem, people wouldn't be doing it so readily, but that's JMHO.
Atho what WRB says can be true, we've rarely removed the cow from the herd or otherwise separated the bull from the calving mother and have had no problems. We've had more problems with the other females and the new calf than with the bull, but not serious problems. If I were a larger operation, I would probably keep all the calving mothers together once I am confident a calf is emminent and on the way just so I can keep a closer eye on them. I have heard of bulls pushing a calf out of the herd or separating it from the mother, but haven't encountered it myself. Personally, I want that new calf to be accepted into the entire herd as quickly as possible by cows and bull.
It would also depend on the size of pasture. Normally a cow will go off by herself to calve and I don't see a problem in this case. However, if she cannot do that, there could be problems with any of the other cows/bulls around, including yearlings who will totally interfer as well.
One other consideration is: when do you want your next calf born? If you like year round calving no worries, but if you don't want a winter calf ect...you might want that bull out of there so that your next crop of calves will be born at your convenience at a time when you can best control the conditions.