How Beneficial Are Prenatal Classes?

I'm on baby number one. while i'm scared, i'm not. I helped my brother raise his two oldest daughters, he was 19 when he had the first, and almost 21 when he had the second, the mother abandoned him with both && i helped him with both his girls since their were babies until their were about 5. they were great birth control! :) but, since i've been pregnant, i've done lots of reading, lots of googling, and i'm just wondering how beneficial are prenatal classes? Have women taken them or not taken them, and what was the outcome?