Pain is a complex neurological response to a range of stressful or damaging stimuli (see IASP definition). Response to a painful stimulus can be mediated by simple spinal cord reflexes while pain perception requires an intact ascending neurological pain pathway and brain development.
The International Association for the Study of Pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage."
Pain in the postnatal human and models for pain perception have been developed and requires conscious recognition or awareness of a noxious stimulus.
In the fetus there are additional hormonal and neurological differences that can impact on pain perception, including the concept of fetal "awareness" (More? see recent review article).
While the neurological pathway of cortico-thalamic connections are found at 24–28 weeks of gestation, "..... Evidence regarding the capacity for fetal pain is limited but indicates that fetal perception of pain is unlikely before the third trimester." (JAMA. 2005 Aug 24;294(8):947-54.)
Page Links: Introduction | Some Recent Findings | Ascending Pain Pathway | References | WWW Links | Glossary
Mellor DJ, Diesch TJ, Gunn AJ, Bennet L. The importance of 'awareness' for understanding fetal pain. Brain Res Brain Res Rev. 2005 Nov;49(3):455-71. ".... endogenous neuro-inhibitors, such as adenosine and pregnanolone, produced within the feto-placental unit that contribute to fetal sleep states, and thus mediate suppression of fetal awareness."
Painful stimulus -> Dorsal Root Ganglion -> Spinal Cord dorsal horn -> Spinothalamic tract (spinal cord, brainstem, midbrain) -> Thalamus (Intralaminar nucleus,Ventroposterior nucleus) -> Cortex (somatosensory S1) / Limbic System / Cingulate Cortex
What is know about development of nociceptors distributed throughout the body? The answer is there is very little literature on human fetal development (some sheep information) of peripheral nociceptors. Newborn infants show strong pain behaviour but it is not clear at what stage fetally that these behavioural responses develop and it should also be noted the difference in fetal "awareness" that could impact upon this response.
Fitzgerald M. The development of nociceptive circuits. Nat Rev Neurosci. 2005 Jul;6(7):507-20.
Rees S, Nitsos I, Rawson J. The development of cutaneous afferent pathways in fetal sheep: a structural and functional study. Brain Res. 1994 Oct 24;661(1-2):207-22.
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Fetal pain perception is unfortunately used by many groups as an emotional, legal and ethical lobby tool.
This current page is a link to resources and information relating to only developmental issues related to the understanding of fetal pain and its relationship to requirements for fetal surgery and anasthesia.
The material is for educational purposes only and cannot be reproduced electronically or in writing without permission.
Please email Dr Mark Hill if you wish to make a comment about this current project.
