If your baby is in a posterior position, his face is turned up toward your belly. This can make labor longer and more difficult, since the widest part of his head has to fit through the birth canal.
You may be able to help your baby rotate into a normal, face-down position by getting on all fours with your bottom in the air, which allows your uterus to drop forward. Your doctor may also try to reposition your baby by reaching in through your vagina and gently rotating his head with his hand or forceps. If none of these methods works, a cesarean section may be needed.