Final answer:
The pain experienced during the first stage of labor, particularly uterine contractions, is primarily transmitted through the Lumbar (L1-L5) dermatomes.
Step-by-step explanation:
The pain experienced during the first stage of labor, particularly uterine contractions, is primarily transmitted through the Lumbar (L1-L5) dermatomes. Uterine contractions during labor are caused by stretching of the myometrium and cervix by the full-term fetus, which triggers reflexive uterine contractions. These contractions result in cervical dilation, and the pain is attributed to myometrial hypoxia during these contractions.