I don't think they are completely necessary, we didn't learn much about delivery really, watched a few vids, discussed pain relief, c-sect vs natural etc, but it was wonderful to meet up with a group of women all having their first bub, and we are still in touch now 7 years later.
Our hospital offered post natal classes, once a week for 6 weeks, and they were brilliant. We were given a first aid course, a dentist came and spoke to us regarding dental care for babies, a phsio came and discussed exercises for babies, there was one day where a speaker from the ABA came though. I didn't BF DS1 but it didn't bother me since I got so much else out of the classes.
Perhaps enquire about post natal classes? Even if you get nothing from them, you will meet some new people and they could be a great support to you over the coming months with your new baby. I used to really look forward to catching up with my mum's group once a week.