I had this with all 3 pregnancies. It's unpleasant, but unlike varicose veins in other places, they do go away after the birth. It wasn't a problem during labour but if it looks like you'll need an episiotomy, it's worth alerting the medical staff if they cut through one of the veins you will lose quite a bit of blood. This happened to me with dd1 it alarmed the staff a bit and made me feel rotten for a while after the birth, but I don't think it was medically dangerous. If you do lose a lot of blood, ask for iron tablets right away, which made a big difference.
In my 2nd and 3rd pregnancies I had tears (quite a big one with my 2nd, who was 10lb!) and there was no problem at all.