Deliver early for twins?

Megan • Pregnant with babies #2&3 after a long (8 years) road with IVF and 4 miscarriages. Ready to enjoy these 9 months!
Hey moms! I was told by my md that because I'm carrying twins, they will deliver me at 38 weeks. I know that can be considered full term, but what if the babies aren't ready and would come naturally at 39 weeks? Wouldn't letting them come when they are ready be more beneficial for their development? Was anyone else told when they would be delivered? (Ps. I hope to deliver as naturally as possible, no epidural, NO c section.)