Supporting the updated definition of pain. But what about labour pain?
The wording of both the current and the authors' proposed definitions of pain describes tissue damage (actual or potential) as the main attributor to the pain experience. The definitions also imply that the function of pain is to indicate bodily tissue damage (actual or potential). Neither of these points may apply to the pain experience associated with labour. During labour, there is undeniably nociceptor activity. Mechanical stimulation of A-delta and C fibres originating in the uterus, cervix, pelvic floor, and surrounding pelvic structures occurs due to strong uterine contractions which dilate the cervix and distend the lower uterine segment to cause descent of the baby through the pelvis.5 This nociception may certainly contribute to a woman's subsequent experience of pain. In fact, it has been demonstrated that pain intensity is associated with degree of cervical dilation and therefore is a useful indicator of progression towards the birth.1,2 It may not be accurate, however, to say that the woman's increasing pain intensity is associated with her perception that there is a rising degree of tissue damage (actual or potential) occurring. It could be argued that as labour is a normal (and essential) physiological process, there is no tissue damage in the sense of injury, pathology, or disease. Instead, there are normal tissue changes occurring. The function of pain in this context could be thought of as an urgent indicator to the woman to tune into her body and focus on the essential and extreme tissue changes that are taking place. It also urges the woman to seek help from caregivers and her pain behaviours signal to caregivers that she is in need of help.6 We accept that childbirth remains a dangerous experience for many women across the world, but is the pain a sign of tissue vulnerability, or more reflective of an innate need to drive the behaviour of the woman and those around her, and the powerful cognitive, emotional, and social influences on the overall experience of pain3,7?
We would also like to comment on the use of the words “unpleasant” and “distressing” in the current and proposed definitions respectively. It has been demonstrated in a number of studies that labour pain can be experienced as a positive pain ie, one that is not distressing but instead is described as empowering and is embraced by the woman experiencing it.4,7 In these studies, women described their pain using positive emotional qualities such as “it felt good”, “it's positive pain”, and “happy pain”, and used other words such as “power”, “strength”, and “sensational ecstasy” for their pain. Therefore, the pain may not necessarily always be an unpleasant experience and, as these examples demonstrate, certainly not always distressing. We are not suggesting that every woman experiences labour pain in this way, but sometimes unique examples of a phenomenon that challenge existing preconceptions about it allow for learning to occur and a subsequent deeper understanding of that phenomenon. Examining labour pain, particularly positive experiences of it, may teach us something new about pain and broaden our current conceptions of it.