Pain in early labour is limited to dermatomes-
T11 T12 L1
S1 S3
L4 L5
L2 L3
Labor pain caused by uterine contractions and cervical dilation is transmitted through visceral afferent sympathetic nerves entering the spinal cord from T10 - L1. Later in labor, perineal stretching transmits painful stimuli through the pudendal nerve and sacral nerves S2 - S4.
Labour - normal, abnormal, malposition, malpresentation and their management