Prelabour pains are mediated through
T11-T12 Pain pathways during labour The pain of labour arises from - Contraction of myometrium, against the resistance of cervix and perineum - Progressive dilatation of the cervix and lower uterine segment - Stretching and compression of pelvic and perineal structures Pain during the, first stage of labour is mostly visceral pain resulting from uterine contractions and cervical dilatation. It is usually confined to the T11-T12 dermatomes during the latent phase but eventually involves the TIO-LI dermatomes as the labour enters the the active phase. The visceral afferent fibres responsible for labour pain travel with sympathetic nerve.fibres.first to the uterine and cervical plexes then through the hypogastric and aoic plexes before entering the spinal cord with the T10-L1 nerve roots. The onset of perineal pain at the end of fist stage signals the beginning of the fetal descent and the second stage of labour. Stretching and compression of pelvic and perineal structures intensify the pain. Sensory innervations of the perineum is provided by the pudendal nerve (S2-S4) so pain during the second stage of labour involves the T10-S4 dermatosomes.
Tit-T12
T2-L3
S1-S3
L3-L4