Sexual diseases do creep in every now and then, but not as often as one might think. Probably most adult entertainment stars have periodic herpes outbreaks, I would suspect, just because so many people carry that disease anyway. They're screened regularly for the more serious diseases such as HIV and that has been effective.
Pregnancy is rare when a person is properly using the pill (such as not on antibiotics or something to negate it). adult entertainment stars don't show up for work every single day or anything, so I would suspect that if I female did not do scenes during the most fertile days of her cycle, along with the pill, that the risk of pregnancy is almost nothing. I'm sure every now and then, someone has been knocked up and I would venture to suspect those pregnancies are usually terminated.