Massages at the spa

Hey all so I have an hour facial at the spa today. It's an hour long and I'll be laying on my back the whole time. They'll give a nice facial with massaging my neck, shoulders, arms and legs. My question is should I be ok for the hour laying on my back or should I ask for something to put under one side so I'm not totally flat on it? I'm not worried about being uncomfortable since his pregnancy I'm more comfortable on my back just worried about the baby cuz I heard it's bad to do that while pregnant and I'm 26w btw.