linguistic:voice_change, linguistic:paraphrasing
Labour pain

There is currently no definitive scientific explanation for why labour is painful. According to studies, during pregnancy, the myometrium (the muscle part of the uterus) is greatly denervated. Stretch receptors in the uterus disappear during pregnancy, and stretch receptors in the cervix disappear at the onset of labour. Consequently, the reason for labour pain has only been theorised, not ascertained. One theory is that the pain results from the buildup of chemicals released during physical exertion. The second leading theory is that the pain results from the vasoconstriction of uterine blood vessels in the myometrium; each contraction squeezes the blood vessels, reducing blood flow and causing some hypoxia.