1: Pain receptors (nociceptors) are present throughout the unborn child’s entire body by no later than 20 weeks after fertilization and nerves link these receptors to the brain’s thalamus and subcortical plate by no later than 20 weeks.
a. Pain receptors (nociceptors) are present throughout the unborn child’s entire body by no later than 20 weeks.
1. Myers, 2004, p.241, para.2, “The first essential requirement for nociception is the presence of sensory receptors, which first develop in the perioral area at approximately 7 weeks gestation and are diffusely located throughout the body by 14 weeks.95”
Myers LB, Bulich LA, Hess, P, Miller, NM. Fetal endoscopic surgery: indications and anaesthetic management. Best Practice & Research Clinical Anaesthesiology. 18:2 (2004) 231-258.
95Smith S. Commission of Inquiry into Fetal Sentience. London: CARE, 1996.
2. Derbyshire, 2010, p.7, para.2, “For the foetus, an existence of ‘pain’ rests upon the existence of a stimulus that poses a threat to tissue, being detected by a nervous system capable of preferentially responding to stimuli that pose a threat to tissue. The entire experience is completely bounded by the limits of the sensory system and the relationship between that system and the stimulus. If pain is conceived of in this manner then it becomes possible to talk of foetal pain anytime between 10 and 17 weeks GA [gestational age] when nociceptors develop and mature, and there is evidence of behavioural responses to touch.”
Note: Derbyshire’s other published works indicate that he believes pain requires subjective human experience, not possible until after birth; nonetheless, he acknowledges this finding.
Derbyshire SW, Foetal pain? Best Practice & Research Clinical Obstetrics and Gynaecology 24:5 (2010) 647-655.
3. Anand, 1987, p.2, para.2, “Cutaneous sensory receptors appear in the perioral area of the human fetus in the 7th week of gestation; they spread to the rest of the face, the palms of the hands, and the soles of the feet by the 11th week, to the trunk and proximal parts of the arms and legs by the 15th week, and to all cutaneous and mucous surfaces by the 20th week.25,26”
Anand KJS, Hickey PR. Pain and its effects in the human neonate and fetus. New England Journal of Medicine. 317:21 (1987) 1321-1329.
25Humphrey T. Some correlations between the appearance of human fetal reflexes and the development of the nervous system. Progress in Brain Research. 4 (1964) 93-135.
26Valnaan HB, Pearson JP. What the fetus feels. British Medical Journal. 280 (1980) 233-234.
4. Vanhatalo, 2000, p.146, col.2, para.2, “First nociceptors appear around the mouth as early as the seventh gestational week; by the 20th week these are present all over the body.”
Vanhalto S, van Nieuwenhuizen O. Fetal Pain? Brain & Development. 22 (2000) 145-150.
5. Brusseau, 2008, p.14, para.3, “The first essential requirement for nociception is the presence of sensory receptors, which develop first in the perioral area at around 7 weeks gestation. From here, they develop in the rest of the face and in the palmar surfaces of the hands and soles of the feet from 11 weeks. By 20 weeks, they are present throughout all of the skin and mucosal surfaces.19
Brusseau R. Developmental Perpectives: is the Fetus Conscious? International Anesthesiology Clinics. 46:3 (2008) 11-23.
19Simons SH, Tibboel D. Pain perception development and maturation. Seminars on Fetal and Neonatal Medicine. 11 (2006) 227-231.
6. Rollins, 2012, p.465, “Immature skin nociceptors are probably present by 10 weeks and definitely present by 17 weeks. Nociceptors develop slightly later in internal organs. Peripheral nerve fibers that control movement first grow into the spinal cord at about 8 weeks of gestation.”
Mark D. Rollins, Mark A. Rosen, “Anesthesia for Fetal Intervention and Surgery”, in Gregory’s Pediatric Anesthesia, ed. George A. Gregory & Dean B. Adropoulos (West Sussex: Wiley-Blackwell, 2012), 444–474, 465.
b. nerves link these receptors to the brain’s thalamus and subcortical plate by no later than 20 weeks.
1. Van Scheltema 2008, p.313, para.1 ― “The connection between the spinal cord and the thalamus (an obligatory station through which nearly all sensory information must pass before reaching the cortex) starts to develop from 14 weeks onwards and is finished at 20 weeks.”
Van Scheltema PNA, Bakker S, Vandenbussche FPHA, Oepkes, D. Fetal Pain. Fetal and Maternal Medicine Review. 19:4 (2008) 311-324.
2. Glover, 1999, p.882, col.1, para.1, “Most incoming pathways, including nociceptive ones, are routed through the thalamus and, as stated above, penetrates the subplate zone from about 17 weeks… These monoamine fibres start to invade the subplate zone at 13 weeks and reach the cortex at about 16 weeks. This puts an early limit on when it is likely that the fetus might be aware of anything that is going on in its body or elsewhere.”
Glover V. Fetal pain: implications for research and practice. British Journal of Obstetrics and Gynaecology. 106 (1999) 881-886.
3. Lee, 2005, p.950, col.1, “In contrast to direct thalamocortical fibers, which are not visible until almost the third trimester, thalamic afferents begin to reach the somatosensory subplate at 18 weeks’ developmental age (20 weeks’ gestational age)16 and the visual subplate at 20 to 22 weeks’ gestational age. These afferents appear morphologically mature enough to synapse with subplate neurons.17”
Note: Lee et al. believe that pain requires conscious cortical processing, which they deem unlikely until 29 or 30 weeks; nonetheless, they acknowledges this finding.
Lee SJ, Ralston HJP, Drey EA, Partridge, JC, Rosen, MA. A Systematic Multidisciplinary Review of the Evidence. Journal of the American Medical Association. 294:8 (2005) 947-954.
16Kostovic I, Rakic P. Developmental history of the transient subplate zone in the visual and somatosensory cortex of the macaque monkey and human brain. Journal of Comparative Neurology. 297 (1990) 441-470.
17Hevner RF. Development of connections in the human visual system during fetal mid-gestation: a Diltracing study. Journal of Experiemental Neuropathology & Experimental Neurology. 59 (2000) 385-392.
4. Gupta, 2008, p.74, col.2, para.1, “ Peripheral nerve receptors develop between 7 and 20 weeks gestation… Spinothalamic fibres (responsible for transmission of pain) develop between 16 and 20 weeks gestation, and thalamocortical fibres between 17 and 24 weeks gestation.”
Gupta R, Kilby M, Cooper G. Fetal surgery and anaesthetic implications. Continuing Education in Anaesthesia, Critical Care & Pain. 8:2 (2008) 71-75.
5. Van de Velde, 2012, p 206, para.3, “To experience pain an intact system of pain transmission from the peripheral receptor to the cerebral cortex must be available. Peripheral receptors develop from the seventh gestational week. From 20 weeks’ gestation [= 20 weeks post-fertilization] peripheral receptors are present on the whole body. From 13 weeks’ gestation the afferent system located in the substantia gelatinosa of the dorsal horn of the spinal cord starts developing. Development of afferent fibers connecting peripheral receptors with the dorsal horn starts at 8 weeks’ gestation. Spinothalamic connections start to develop from 14 weeks’ and are complete at 20 weeks’ gestation, whilst thalamocortical connections are present from 17 weeks’ and completely developed at 26–30 weeks’ gestation. From 16 weeks’ gestation pain transmission from a peripheral receptor to the cortex is possible and completely developed from 26 weeks’ gestation.”
Marc Van de Velde & Frederik De Buck, Fetal and Maternal Analgesia/Anesthesia for Fetal Procedures. Fetal Diagn Ther 31(4) (2012) 201-9.