The Relief of Pain in Labour

During the first stage the pain arises from the uterus,cervix and upper vagina passes through Frankenhouser's ganglion to the hypogastric and thenthe pre-aortic plexuses to enter the spinal cord.
The pain is do to increased pressure with each contraction and due to cervical dilatation.
The highest degree of pain is felt during the transitional period between the first and second stage.

During the second stage the pain arises from the vagina and perineum is transmitted through the pudendal nerves to enter the spinal cord.

See LABOUR STAGES