I had one with both my girls. With DD1 it was practically instant, I was pain free within seconds it felt. I got cold shivers as a side effect though. It worked well though. With DD2 it took longer to kick in (around 15 minutes) and as she arrived so quickly (37 minute labour!), I felt everything and the epidural took effect after she was born. Although very painful, it was great to experience the 'ring of fire' when she crowned but annoying to be pain free just after she arrived and therefore bed ridden until it wore off. I didn't get the shivers that time though.