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Foetal pain?
Best Practice & Research Clinical Obstetrics and Gynaecology 24 (2010) 647–655
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Foetal pain? Stuart W.G. Derbyshire, PhD, Senior Lecturer * University of Birmingham, School of Psychology, Edgbaston B15 2TT, UK
Keywords: Pain nociception abortion surgery human development consciousness awareness foetal
The majority of commentary on foetal pain has looked at the maturation of neural pathways to decide a lower age limit for foetal pain. This approach is sensible because there must be a minimal necessary neural development that makes pain possible. Very broadly, it is generally agreed that the minimal necessary neural pathways for pain are in place by 24 weeks gestation. Arguments remain, however, as to the possibility of foetal pain before or after 24 weeks. Some argue that the foetus can feel pain earlier than 24 weeks because pain can be supported by subcortical structures. Others argue that the foetus cannot feel pain at any stage because it is maintained in a state of sedation in the womb and lacks further neural and conceptual development necessary for pain. Much of this argument rests on the definition of terms such as ‘wakefulness’ and ‘pain’. If a behavioural and neural reaction to a noxious stimulus is considered sufficient for pain, then pain is possible from 24 weeks and probably much earlier. If a conceptual subjectivity is considered necessary for pain, however, then pain is not possible at any gestational age. Regardless of how pain is defined, it is clear that pain for conceptual beings is qualitatively different than pain for nonconceptual beings. It is therefore a mistake to draw an equivalence between foetal pain and pain in the older infant or adult. Ó 2010 Elsevier Ltd. All rights reserved.
During the past 10 years there has been increasing legislative interest in the possibility of foetal pain. In 2006, the US House of Representatives debated the Unborn Child Pain Awareness Act.1 The bill secured a majority but failed to obtain the two-thirds majority necessary to pass it as a law. Efforts at the state level have been more successful. At least 25 US states have deliberated on foetal pain
* Tel.: þ44 0121 414 4659; Fax: þ44 0121 414 4897. E-mail address: [email protected] 1521-6934/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.bpobgyn.2010.02.013
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legislation and at least eight (Alaska, Arkansas, Georgia, Oklahoma, South Dakota, South Louisiana, Texas and Wisconsin) now have legislation requiring that women seeking abortions be informed of the possibility of foetal pain. Foetal pain has also been widely debated in Britain. The British Medical Research Council (MRC) and the Royal College of Obstetricians (RCOG) have both issued reports on this subject2,3; the issue of foetal pain was debated upon by the British Parliamentary Science and Technology Select Committee in 2008.4 To the author’s knowledge, however, no British or European legislation makes any direct reference to foetal pain. Increasingly invasive surgical and other medical procedures performed in utero have also generated contemporary interest in foetal pain. Although rare, it is now possible to perform foetal surgery for conditions such as lower urinary tract obstruction, hydrothorax, cystic adenomatous malformation of the lung, congenital diaphragmatic hernia, spina bifida and large sacrococcygeal teratomas.5 More commonly, but still relatively rare, the foetus may be exposed to invasive interventions for the transfusion of donor red cells into the foetal intrahepatic umbilical vein or the peritoneal cavity. In addition, drainage of abnormal fluid collections, for example, a dilated bladder or hydrothorax, can be achieved by a single aspiration using a needle or the percutaneous insertion of an indwelling shunt into the amniotic cavity. Similarly, endoscopic placement of a balloon that is inflated in the foetal trachea can be used to improve outcome in cases of congenital diaphragmatic hernia. Finally, surgical abortion can obviously expose the foetus to intensely invasive procedures. Resolving the question as to whether the foetus feels pain is not straightforward, most attempts at answering the question consider the neural pathways that are necessary for pain and ask when those pathways are present and functional in the foetus.6–10 This approach is useful because it is reasonable to assume that there is a necessary neural biology that renders pain experience possible. If the foetus lacks that necessary neural biology then it is reasonable to assume that it cannot feel pain. The approach is limited, however, by knowledge of the necessary neural biology. Although there is a general consensus that certain cortical structures are necessary for pain, legitimate arguments that cortical structures are not necessary continue to be raised.9,11,12 This article will first consider the neural pathways that might be necessary for pain and then go on to consider the limitations of deciding foetal pain based on the existence of such pathways. The neuroanatomy of pain A considerable amount is known about the biological structures involved in painful experience. Humans, and many other species, have neural structures that respond preferentially to noxious stimuli.13–15 Beginning in the periphery, there are nerve endings that preferentially transmit noxious information. They are the free nerve endings that arise mostly from the peripheral termination of A-delta and C fibres. The free nerve endings are polymodal and can respond to non-noxious and noxious temperatures or mechanical stimuli. When activity in A-delta and C fibres gives rise to pain or behaviour associated with pain then they are labelled as nociceptors. Fibres that only respond in the noxious range are labelled as nociceptive specific, while those that respond across the noxious and non-noxious range are labelled as wide dynamic range. The primary afferent A-delta and C fibres terminate on neurons in the superficial dorsal horn of the spinal cord. Ascending projections to the thalamus originate from the most superficial layer, known as lamina I, and project contralaterally in the spinothalamic tract (STT). Intracellular recordings from lamina I neurons revealed neurons with seemingly modality-specific responses. One class of neurons were nociceptive specific, responsive only to noxious pinch, heat or both. Another class were thermoreceptive-specific, responding only to non-noxious cooling. A final class were polymodal, responding to heat, pinch and cooling. Provocatively, the existence of lamina I neurons, with specific responses and distinct morphology, motivated the suggestion that there are dedicated pathways for pain and temperature detection.14 A series of neuroimaging studies have demonstrated consistent activation of several cerebral structures during pain.16 These structures include the primary and secondary somatosensory cortices and anterior cingulate, prefrontal and insular cortices. In combination, these structures are thought to coordinate defensive reactions and generate the sensory and unpleasant feelings associated with pain.
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Thus, a noxious stimulus sets in motion a train of biological events that acts to prevent further injury. People who lack nociceptors or have other biological deficits associated with the nociceptive system do not engage in defensive behaviours and do not report experiences of pain.13 Consequently, they suffer considerable, often life-threatening, injuries. The first evidence for an intact nociceptive system in the foetus emerges at about 8 weeks gestational age (GA). At this stage, touching the perioral region will result in movement away, indicating the presence of sensory receptors and, at least, spinal or brainstem-mediated reflex action.17 Some claim that by 8 weeks GA, there are connections from the periphery and through the spinal cord to the thalamus (http://www.abortionfacts.com/online_books/love_them_both/why_cant_we_love_them_ both_14.asp) but these claims are yet to receive any peer-reviewed verification. At 8 weeks GA, the foetal brain is profoundly immature. There is no indication of maturation such as cortical sulcation and gyration18 or the appearance of a laminar structure in either the thalamus or the cortex.19,20 The external wall of the brain is about 1 mm thick, consisting of an inner and outer layer, but without a cortical plate from which the cortical layers will later develop.21 The cell density of the outer layer is significantly higher than that of a newborn or adult but contains large neurons that resemble those described in the older foetus. Beginning from about 9 weeks GA, there is thalamic fibre penetration directly into this outer layer that stimulates development and maturation of these large neurons.20 There is speculation that by 11 weeks GA these projections may be functional. The possibility of functional neurons from the periphery, into the thalamus and into the outer layer of the developing cortex places a lower time limit for foetal pain at around 11 weeks GA. Between 12 and 18 weeks, the formation of the subplate begins and the first projections from the thalamus into the subplate appear.21–23 The subplate is a transient brain structure formed directly underneath the developing cortical plate. Neurons arrive in the subplate and are held for several weeks until the cortical plate becomes growth-permissive and facilitates neuronal invasion of the cortical plate.24 The relocation of neurons from the subplate to the cortical plate begins around 24 weeks GA and is extremely rapid from about 34 weeks. Afterwards the extracelluar matrix and other growth-related and guidance molecules disappear leading to the dissolution of the subplate.21 Morphological features of maturity can be gradually observed from about 12 weeks GA. At 13 weeks, for example, a linear furrow or groove can be observed at the limit of the temporal lobe below and the insula, frontal and parietal lobes above.18 Around 15 weeks GA, this groove becomes part of the insular cortex, which is believed to be the first lateral cortical region to develop and is a key region involved in the experience of pain.16 The subplate has also been observed to thin in areas where cortical folding occurs, such as the parieto-occipital sulcus, and in the insula and cingulate gyrus at least from 20 weeks GA.25 It is currently uncertain whether this thinning is due to earlier maturation of these regions, and potentially earlier synaptic activity in the insula and cingulate cortex, which are both key areas in the experience of pain16, or due to incidental morphological changes. Nevertheless, before 26 weeks GA, the foetal brain is largely smooth with only minor evidence of sulcation and gyration. Massive growth of the brain after 34 weeks rapidly results in the characteristic folds and surface features of the more mature brain. By 24 weeks GA, substantial thalamocortical afferents have accumulated at the superficial edge of the subplate, which is the stepping-off point for axons growing towards their final cortical targets.21 Between 24 and 32 weeks there is substantial ingrowth of thalamocortical axons in the cortical plate of the frontal, somatosensory, visual and auditory cortex and formation of the first synapses in the deep cortical plate. Clear evidence of synaptic activity following auditory stimulation has been recorded from around 26 weeks in utero and somatosensory responses have been recorded in premature neonates of 25 weeks GA following a noxious heel lance.26,27 By around 24 weeks GA, therefore, it can be assumed that noxious peripheral events cause a response in the primary sensory cortex indicating the presence of a spinothalamic connection. Long axonal tracts now course from the periphery and through the brain to the cortex. It is generally accepted that the necessary neural structures for pain are in place and are functional by 24 weeks GA.6–10 Thus, it is possible that measures to prevent pain might be appropriate during invasive procedures after 24 weeks GA.
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Further developments Recently, however, it has become clear that the pre- and post-birth environments are very different with potentially important consequences for painful experiences. It is also becoming clear that completion of the major pathways from the periphery to the cortex, at around 24 weeks GA, does not signal the end of cortical development but rather the beginning of a further maturational process. In an extensive and important review, Mellor et al. 28 described evidence suggesting that the foetus never enters a state of wakefulness in utero. This conclusion was based largely on observations of foetal lambs. Rigatto et al. 29, for example, directly observed an unanaesthetised sheep foetus, in utero, through a Plexiglas window, for a total of 5000 h without observing signs of wakefulness such as eyes opening or coordinated movement of the head. Mellor and colleagues suggest several factors explain this lack of wakefulness including the environment of the womb, which is warm, buoyant and cushioned, and the presence of a chemical environment that preserves a continuous sleep-like unconsciousness or sedation. The environment of the womb and the chemical suppression of wakefulness maintain unconsciousness and suppress higher cortical activation in the presence of intrusive external stimulation. The foetal response to hypoxia and asphyxia, for example, is characterised by apnoea, cessation of foetal body movements and a shift to a more quiescent Electroencephalographic (EEG) state indicative of unconsciousness.30,31 A series of studies have also demonstrated that as spinothalamic pathways complete their connections with the cortex, from around 24 weeks GA, they increasingly stimulate intracortical pathways into development, which is the next major phase of neuronal maturation. This phase involves elaboration of dendrites and axons, formation and regression of synaptic connections and selective elimination of cell populations and corresponds to the cortical maturation described by Goldman-Rakic32 in primates and by Chugani33 in humans. McKinstry et al. 34 illustrated the effects of this development using diffusion tensor imaging (DTI) in neonates born at 26 and 35 weeks GA. Neonates born at 26 weeks GA have a cortical cell structure dominated by radially orientated dendrites that inhibit the spread of water parallel to the surface of the brain. Consequently, DTI measures an elongated diffusion of water in the cortex. Neonates born at 35 weeks GA, in contrast, have a cortical cell structure with radially orientated and basal dendrites that inhibit the spread of water in all directions. Consequently, DTI measures a spherical diffusion of water in the cortex. This proliferation of cortical neurons and the overproduction of their arborisation and synaptic contacts begins prenatally, as illustrated by McKinstry et al.34, but continues postnatally, along with synaptic elimination, pruning and programmed cell death.32,33,35,36 The sedation of the foetus in utero, and the further development of the cortex, which only completes after birth, imply that it is only after birth, when the infant awakens and cortical development completes, that pain will be experienced. To put that slightly differently, it is seemingly reasonable, given the immature nature of the foetus and the apparent lack of wakeful activity, to reject the possibility of foetal pain on the grounds of pain being objectively impossible in utero. The meaning of biological immaturity The conclusion that the foetus cannot experience pain at any stage of development has met with considerable resistance.9,11 Opponents point out that the cortex might not be the only neural structure capable of processing pain. Subcortical structures, such as the brainstem, for example, respond to noxious stimulation. Subcortical responses occur in response to needling from 18 weeks GA.36 In addition, anencephalic infants, who typically lack almost the entire cortex, demonstrate a capacity to learn and show evidence of emotion12,37, which supports the possibility of some kind of brainstemmediated pain experience.11 An anencephalic foetus also withdraws from noxious stimulation, demonstrating that withdrawal is mediated at a subcortical level.38 Infants with significant neonatal neurological injury due to a parenchymal brain injury also respond to noxious stimulation with a pattern of biobehavioural and facial reactions similar to infants without brain injury.39 If the foetus is sedated and asleep in the womb then it might be possible to dispense with all arguments based on neurobiology because it is typically assumed that a sleeping organism cannot feel. Mellor et al. 28 propose that the foetus is unconscious based on the presence of powerful sedating
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chemicals in the womb (most notably adenosine), the presence of sleep-like EEG patterns observed in the lamb foetus that enter a more quiescent state during stress, and a lack of movement during stress. Unfortunately, these conditions do not guarantee or dictate a lack of wakefulness. Relaxation and sleep can be broken by noxious stimuli40 and although the EEG activity in the lamb foetus enters a state of relative quiescence during stress (such as caused by umbilical cord occlusion) there are clear indications of large spikes within that quiescence.31 Rather than EEG silence during stress, there is a shift from one EEG pattern to another and we have no direct means of assessing what either pattern means in terms of experience. It is also questionable whether the stress of umbilical cord occlusion is comparable to the nociceptive stress that will occur during surgery. A series of studies with rats have also demonstrated that mammalian foetal behaviour is complex and organised. Foetal behaviour includes temporal rhythmicity, movement synchrony and motor coordination that are related to postnatal grooming, suckling and locomotor behaviour.41–44 The rat foetus responds vigorously to chemical stimulation, such as a lemon infusion, and preconditioning with other chemical stimulation, such as mint, modifies these responses.45 Human foetuses also detect and respond to chemical stimuli46, move away when approached with a scalpel or needle during surgical procedures47 and show evidence of learning in utero.48,49 While these responses might occur during a state of sleep or sedation they are certainly not incompatible with wakefulness. Associating EEG patterns during gestation with sleep-like states is also difficult because there is, in general, no clear cut-off between conscious and unconscious EEG activity.50,51 For the neonate, and presumably the foetus, sleep is accompanied by ongoing background EEG without obvious differences between wake and sleep.52,53 These observations of cortical activity during ‘sleep’ in the neonate raise the question of what ‘sleep’ and ‘wakefulness’ actually mean for the neonate or foetus. A subcortical response to noxious stimulation and lack of uncertainty regarding the nature of foetal consciousness makes a definitive rejection of foetal pain difficult. The difficulty stems not just from a lack of neuroscientific knowledge but also from a lack of substance with regard to the nature of sensory experience. Without a satisfactory or comprehensive approach to the nature of sensory experience, terms such as ‘awake’ or ‘conscious’ or ‘pain’ and so forth take on a somewhat arbitrary character and can be attached to any apparently coherent neural behaviour. Certain patterns of EEG activity might or might not be associated with being awake; certain neuronal activity might or might not be associated with being conscious; and certain areas of the brain might or might not be necessary for pain. There is no means of deciding these issues without an adequate account of the subjective terms in use. Why the definition of pain is critical How we define pain is critical. Defining pain as the response to noxious stimulation might seem sensible until it is realised that such a definition will allow almost anything to be in pain because even rocks respond to violent force by shattering and thermostats respond to high temperatures by changing their internal state. Allowing rocks and thermostats to have a pain response is much too permissive. Furthermore, a definition of pain based on response leads to a tautological understanding of pain. Pain is defined in terms of a stimulus that is deemed to be painful because it elicits the pain response. Put simply: pain is defined as pain.54,55 A definition of pain that includes the content of pain is required to avoid tautology. Definitions of pain that avoid tautology usually include cognition, sensation and affective processes such as that provided by the International Association for the Study of Pain (IASP).56 The IASP have defined pain as ‘‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life.’’ By this definition, pain is no longer regarded as merely a physical sensation of noxious stimulus and disease but is seen as a conscious experience which may be modulated by mental, emotional and sensory mechanisms and includes both sensory and emotional components. The multidimensional emphasis and reference to subjectivity makes it difficult to deny an active cortical role for pain experience. Suppression of cortical activity is widely associated with profound loss of conscious experience.57 For pain to be supported by subcortical structures, therefore, requires that pain be redefined as something less than a multidimensional, subjective experience.
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Those that support the possibility of foetal pain have made attempts to change the IASP definition of pain.58 Those efforts have largely focussed on removing the apparent requirement for language from the definition and resulted in a new note being added to the IASP definition: ‘‘The inability to communicate verbally does not negate the possibility that an individual is experiencing pain and is in need of appropriate pain-relieving treatment.’’ The note clarifies that being unable to talk does not mean a person is unable to experience pain but it does not change the substance of the IASP definition. It is unlikely that the efforts to change the IASP definition were intended to clarify something as obvious as silence not delivering pain relief. Presumably, the intention was to reduce the requirements for pain experience so that pain could be more easily attributed to inherently, rather than temporarily, non-verbal beings such as the foetus. Rather than something multidimensional and subjective, pain is reduced to a physical, raw nature by stripping away the layers of conceptualisation that we associate with language. The challenge is to understand pain as something apprehended rather than comprehended. Pain is something that just is, an experience that is complete but irreducible and immediate: a pure immediacy that cannot be allowed any durability. Conceptual, language-ridden beings such as persons cannot experience sensation as a pure immediacy. Sensory experiences in conceptual beings are propositional. Such beings are not merely in pain but know that they are in pain. Knowing that I am in pain involves concepts – ‘sore’, ‘stabbing’, ‘damage’, ‘threat’ and ‘body’ – that are themselves rooted in general beliefs. For conceptual beings, there is no such thing as a pure pain experience that can be extracted from those general beliefs. Every painful experience will invoke its own set of autobiographical associations and expectations that form both the content and the context of the pain experience. Conceptual beings cannot return to a more innocent, aconceptual state. Perception in conceptual beings is structured by concepts and categories from language and thought and is directed towards what is recognised as threatening or desirable. The perceptual field no longer dictates behaviour or experience because conceptual beings highlight the structurally relevant elements, keeping the correct components together and the incorrect components apart. Perception demands a flow of interpretation that informs and constitutes the experience. Every experience that a conceptual being has will follow and be dependent upon a period of conceptual development. The foetus has no options regarding its behaviour in the presence of noxious stimuli. It cannot, for example, decide it is in his/her best interests to remain still during surgery any more than he/she can launch a protest against an abortion. The foetus must react according to the dictates of its biology in the presence of an eliciting stimulus. Anything further will require a conceptual apparatus that will be provided as language and higher forms of thought and behavioural organisation become possible through development. The suggestion that the foetus can feel an equivalent pain to that of an older, conceptual infant misses or denies the necessary role of development in constructing sensorial experience. Nevertheless, the question remains, what is sensation before conceptual development? Sensation before conceptual development Insisting that only conceptual beings have the apparatus to engage in sensation means denying sensation to all animals and all infants less than approximately 2–3 months of age. Such a position strikes many as implausible.9,12,58,59 As discussed earlier in this article, one possible way to avoid the conclusion that only human beings of a certain advanced age experience sensation is to define sensation as something raw and pure. Animals and the foetus might have a perceptual sensitivity to features of the environment that are entirely contained within nature. What exists in animals and the foetus also exists in conceptual beings but perceptual sensitivity in conceptual beings is taken up into the ambit of consciousness where raw immediacy becomes abstract experience.59 Even in non-verbal, aconceptual, creatures, however, there is more to perceptual sensitivity than merely neural activity.60,61 The visual system endows objects, for example, with colour in the same sense that cows endow grass with the character of food. Grass is food for cows because cows eat grass. If cows did not eat grass then grass would not be food. The existence of grass as a food for cows depends upon the relationship between cows and grass and that relationship cannot be reduced to a neural event because the neural event is only one part of the story.
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Sensory perception might be viewed in the same way. Sensations are not projected into objects, which cannot sense, but sensations arise through a relation with the object. That relationship makes the appearance and existence of the object, as qualities of the object, possible. Colours, for example, inhere in objects only by virtue of their relations with a being perceptually sensitive to colour. In similar fashion, noxious stimuli are painful only by virtue of their contact with a being perceptually sensitive to stimuli in the noxious range. The entire experience is more than just nervous tissue activity even though the physiological or sensory structure of the perceptually sensitive being determines the experienced content of the stimulus. This observation is important because it allows us to potentially say that the foetus feels pain without forcing us to also say that rocks and thermostats feel pain. 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 when nociceptors develop and mature, and there is evidence of behavioural responses to touch.35 Further developments of the nervous system then provide for alterations or elaborations of the pain response; each development potentially provides what some have called an experience of pain relevant to that stage of development.9,58 Conclusions Decisions regarding foetal pain are typically resolved by reference to neuroanatomy. Before the presence of a system capable of detecting noxious events, it is reasonable to deny the possibility of pain in utero. Deciding the minimally necessary neuroanatomy, however, is not straightforward. There is considerable disagreement regarding the contribution of the cortex and the possibility of pain, and other conscious experiences, being supported subcortically. One reason for this disagreement is the lack of precision in defining what is meant by ‘pain’. If pain is defined in terms of a noxious stimulus being detected by a nervous system that can preferentially respond to stimuli in the noxious range then pain can be attributed to the foetus from around 10 weeks GA. However, if pain is defined as an elaborate multidimensional experience that is subjective, then pain can never be attributed to the foetus because it is implausible to attribute that much conceptual activity to the foetus.61 This review is agnostic with regard to which view of pain is ‘correct’. It is possible that both views are correct or both views are incorrect but it is not possible that both views are equivalent. Pain in a conceptual being is both apprehended and comprehended whereas pain in a non-conceptual being is, at most, only apprehended. Once pain is comprehended, there is no return to a more innocent state of apprehension. Sensory experience for conceptual beings is not the product of raw experiences stacked together but is a profoundly different way of experiencing the world. Pain for the foetus, whatever that might feel like, will be bounded by the activity in dedicated neural pathways set in motion by a stimulus in the noxious range. The foetus just is, and his experiences just are, and they just are without further regard. Pain for the conceptual infant, in contrast, will open out into the unfolding of his or her life to be connected with a vast array of other sensations, emotions and understanding of the world and the self. The conceptual being has a self-existence that has great regard towards all experience.
Practice points There are numerous surgical procedures, in addition to surgical abortion, that may induce foetal pain but that remains uncertain. The uncertainty regarding foetal pain means that any direction to change clinical practice based on foetal pain would be premature. The use of analgesia or anaesthetic during in utero procedures should remain at the discretion of the medical team responsible for the procedures.
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Research agenda Clinical trials evaluating the clinical benefit of analgesia or anaesthesia during in utero procedures. Neural development in utero. Psychological investigations of sentient versus propositional sensory experience.
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*35. Fitzgerald M. The development of nociceptive circuits. Nat Rev Neurosci 2005; 6: 507–520. 36. Giannakoulopoulos X, Sepulveda W, Kourtis P et al. Fetal plasma cortisol and b;-endorphin response to intrauterine needling. Lancet 1994; 344: 77–81. 37. Tuber DS, Berntson GB, Bachman DS et al. Associative learning in premature hydranencephalic and normal twins. Science 1980; 210: 1035–1037. 38. Visser GH, Laurini RN, de Vries JIP et al. Abnormal motor behaviour in anencephalic fetuses. Early Hum Dev 1985; 12: 173–182. 39. Oberlander TF, Grunau RE, Fitzgerald C et al. Does parenchymal brain injury affect biobehavioral pain responses in very low birth weight infants at 32 weeks’ postconceptional age? Pediatrics 2002; 110: 570–576. 40. Nofzinger EA & Derbyshire SWG. Pain imaging in relation to sleep. In Lavigne G, Sessle BJ, Choiniere M & Soja PJ (eds.). Sleep and pain. IASP Press, 2007, pp. 153–173. 41. Smotherman WP & Robinson SR. Environmental determinants of behaviour in the rat fetus. Anim Behav 1986; 37: 1859–1873. 42. Robertson SS. Cyclic motor activity in the human fetus after midgestation. Dev Psychobiol 1985; 18: 411–419. 43. Robinson SR & Smotherman WP. Environmental determinants of behaviour in the rat fetus: II. The emergence of synchronous movement. Anim Behav 1987; 35: 1652–1662. 44. Beckoff A & Lau B. Interlimb coordination in 20-day-old rat fetuses. J Exp Zool 1980; 214: 173–175. 45. Smotherman WP & Robinson SR. Behavior of rat fetuses following chemical or tactile stimulation. Behav Neurosci 1988; 102: 24–34. 46. Brown JV. Chemosensory development in the fetus and newborn. Newborn Infant Nurs Rev 2008; 8: 180–186. 47. Williams C. Framing the fetus in medical work: rituals and practices. Soc Sci Med 2005; 60: 2085–2095. 48. DeCaspar AJ & Fifer WP. Of human bonding: newborns prefer their mother’s voices. Science 1980; 208: 1174–1176. 49. Hepper PG. Foetal ‘‘soap’’ addiction. Lancet 1988; 1: 1347–1348. 50. Niedermeyer E. Maturation of the EEG: development of waking and sleep patterns. In Niedermeyer E & Da Silva FL (eds.). Electroencephalography: basic principles, clinical applications, and related fields. 5th edn. Philadelphia: Lipincott, Williams and Wilkins, 2005, pp. 209–234. 51. Vickers MD. Final discussion and conclusions. In Rosen M & Lunn JN (eds.). Consciousness, awareness, and pain in general anaesthesia. London: Butterworths Press, 1987, pp. 180–183. 52. de Weerd AW & van den Bossche AS. The development of sleep during the first months of life. Sleep Med Rev 2003; 7: 179–191. 53. Ellingson R. Variability of visually evoked responses in the human newborn. Electroencephalogr Clin Neurophysiol 1970; 29: 10–19. 54. Derbyshire SWG. The IASP definition captures the essence of pain experience. Pain Forum 1999; 8: 106–109. 55. Wall PD. Why the definition of pain is crucial. In Wall P & Melzack R (eds.). Textbook of pain. Churchill Livingstone, 1989, pp. 1–18. 56. Merskey H. The definition of pain. Eur Psychiatry 1991; 6: 153–159. 57. Baars BJ, Ramsoy TZ & Laureys S. Brain, conscious experience and the observing self. Trend Neurosci 2003; 26: 671–675. 58. Anand KJS & Craig KD. New perspectives on the definition of pain. Pain 1996; 67: 3–6. 59. McDowell J. Mind and World. London: Harvard University Press, 1996. 60. Mead GH. Mind, self and society. Chicago: University of Chicago Press, 1934. 61. Tallis R. The knowing animal: a philosophical inquiry into knowledge and truth. Edinburgh: Edinburgh University Press, 2005.
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Foetal pain? Stuart W.G. Derbyshire, PhD, Senior Lecturer * University of Birmingham, School of Psychology, Edgbaston B15 2TT, UK
Keywords: Pain nociception abortion surgery human development consciousness awareness foetal
The majority of commentary on foetal pain has looked at the maturation of neural pathways to decide a lower age limit for foetal pain. This approach is sensible because there must be a minimal necessary neural development that makes pain possible. Very broadly, it is generally agreed that the minimal necessary neural pathways for pain are in place by 24 weeks gestation. Arguments remain, however, as to the possibility of foetal pain before or after 24 weeks. Some argue that the foetus can feel pain earlier than 24 weeks because pain can be supported by subcortical structures. Others argue that the foetus cannot feel pain at any stage because it is maintained in a state of sedation in the womb and lacks further neural and conceptual development necessary for pain. Much of this argument rests on the definition of terms such as ‘wakefulness’ and ‘pain’. If a behavioural and neural reaction to a noxious stimulus is considered sufficient for pain, then pain is possible from 24 weeks and probably much earlier. If a conceptual subjectivity is considered necessary for pain, however, then pain is not possible at any gestational age. Regardless of how pain is defined, it is clear that pain for conceptual beings is qualitatively different than pain for nonconceptual beings. It is therefore a mistake to draw an equivalence between foetal pain and pain in the older infant or adult. Ó 2010 Elsevier Ltd. All rights reserved.
During the past 10 years there has been increasing legislative interest in the possibility of foetal pain. In 2006, the US House of Representatives debated the Unborn Child Pain Awareness Act.1 The bill secured a majority but failed to obtain the two-thirds majority necessary to pass it as a law. Efforts at the state level have been more successful. At least 25 US states have deliberated on foetal pain
* Tel.: þ44 0121 414 4659; Fax: þ44 0121 414 4897. E-mail address: [email protected] 1521-6934/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.bpobgyn.2010.02.013
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legislation and at least eight (Alaska, Arkansas, Georgia, Oklahoma, South Dakota, South Louisiana, Texas and Wisconsin) now have legislation requiring that women seeking abortions be informed of the possibility of foetal pain. Foetal pain has also been widely debated in Britain. The British Medical Research Council (MRC) and the Royal College of Obstetricians (RCOG) have both issued reports on this subject2,3; the issue of foetal pain was debated upon by the British Parliamentary Science and Technology Select Committee in 2008.4 To the author’s knowledge, however, no British or European legislation makes any direct reference to foetal pain. Increasingly invasive surgical and other medical procedures performed in utero have also generated contemporary interest in foetal pain. Although rare, it is now possible to perform foetal surgery for conditions such as lower urinary tract obstruction, hydrothorax, cystic adenomatous malformation of the lung, congenital diaphragmatic hernia, spina bifida and large sacrococcygeal teratomas.5 More commonly, but still relatively rare, the foetus may be exposed to invasive interventions for the transfusion of donor red cells into the foetal intrahepatic umbilical vein or the peritoneal cavity. In addition, drainage of abnormal fluid collections, for example, a dilated bladder or hydrothorax, can be achieved by a single aspiration using a needle or the percutaneous insertion of an indwelling shunt into the amniotic cavity. Similarly, endoscopic placement of a balloon that is inflated in the foetal trachea can be used to improve outcome in cases of congenital diaphragmatic hernia. Finally, surgical abortion can obviously expose the foetus to intensely invasive procedures. Resolving the question as to whether the foetus feels pain is not straightforward, most attempts at answering the question consider the neural pathways that are necessary for pain and ask when those pathways are present and functional in the foetus.6–10 This approach is useful because it is reasonable to assume that there is a necessary neural biology that renders pain experience possible. If the foetus lacks that necessary neural biology then it is reasonable to assume that it cannot feel pain. The approach is limited, however, by knowledge of the necessary neural biology. Although there is a general consensus that certain cortical structures are necessary for pain, legitimate arguments that cortical structures are not necessary continue to be raised.9,11,12 This article will first consider the neural pathways that might be necessary for pain and then go on to consider the limitations of deciding foetal pain based on the existence of such pathways. The neuroanatomy of pain A considerable amount is known about the biological structures involved in painful experience. Humans, and many other species, have neural structures that respond preferentially to noxious stimuli.13–15 Beginning in the periphery, there are nerve endings that preferentially transmit noxious information. They are the free nerve endings that arise mostly from the peripheral termination of A-delta and C fibres. The free nerve endings are polymodal and can respond to non-noxious and noxious temperatures or mechanical stimuli. When activity in A-delta and C fibres gives rise to pain or behaviour associated with pain then they are labelled as nociceptors. Fibres that only respond in the noxious range are labelled as nociceptive specific, while those that respond across the noxious and non-noxious range are labelled as wide dynamic range. The primary afferent A-delta and C fibres terminate on neurons in the superficial dorsal horn of the spinal cord. Ascending projections to the thalamus originate from the most superficial layer, known as lamina I, and project contralaterally in the spinothalamic tract (STT). Intracellular recordings from lamina I neurons revealed neurons with seemingly modality-specific responses. One class of neurons were nociceptive specific, responsive only to noxious pinch, heat or both. Another class were thermoreceptive-specific, responding only to non-noxious cooling. A final class were polymodal, responding to heat, pinch and cooling. Provocatively, the existence of lamina I neurons, with specific responses and distinct morphology, motivated the suggestion that there are dedicated pathways for pain and temperature detection.14 A series of neuroimaging studies have demonstrated consistent activation of several cerebral structures during pain.16 These structures include the primary and secondary somatosensory cortices and anterior cingulate, prefrontal and insular cortices. In combination, these structures are thought to coordinate defensive reactions and generate the sensory and unpleasant feelings associated with pain.
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Thus, a noxious stimulus sets in motion a train of biological events that acts to prevent further injury. People who lack nociceptors or have other biological deficits associated with the nociceptive system do not engage in defensive behaviours and do not report experiences of pain.13 Consequently, they suffer considerable, often life-threatening, injuries. The first evidence for an intact nociceptive system in the foetus emerges at about 8 weeks gestational age (GA). At this stage, touching the perioral region will result in movement away, indicating the presence of sensory receptors and, at least, spinal or brainstem-mediated reflex action.17 Some claim that by 8 weeks GA, there are connections from the periphery and through the spinal cord to the thalamus (http://www.abortionfacts.com/online_books/love_them_both/why_cant_we_love_them_ both_14.asp) but these claims are yet to receive any peer-reviewed verification. At 8 weeks GA, the foetal brain is profoundly immature. There is no indication of maturation such as cortical sulcation and gyration18 or the appearance of a laminar structure in either the thalamus or the cortex.19,20 The external wall of the brain is about 1 mm thick, consisting of an inner and outer layer, but without a cortical plate from which the cortical layers will later develop.21 The cell density of the outer layer is significantly higher than that of a newborn or adult but contains large neurons that resemble those described in the older foetus. Beginning from about 9 weeks GA, there is thalamic fibre penetration directly into this outer layer that stimulates development and maturation of these large neurons.20 There is speculation that by 11 weeks GA these projections may be functional. The possibility of functional neurons from the periphery, into the thalamus and into the outer layer of the developing cortex places a lower time limit for foetal pain at around 11 weeks GA. Between 12 and 18 weeks, the formation of the subplate begins and the first projections from the thalamus into the subplate appear.21–23 The subplate is a transient brain structure formed directly underneath the developing cortical plate. Neurons arrive in the subplate and are held for several weeks until the cortical plate becomes growth-permissive and facilitates neuronal invasion of the cortical plate.24 The relocation of neurons from the subplate to the cortical plate begins around 24 weeks GA and is extremely rapid from about 34 weeks. Afterwards the extracelluar matrix and other growth-related and guidance molecules disappear leading to the dissolution of the subplate.21 Morphological features of maturity can be gradually observed from about 12 weeks GA. At 13 weeks, for example, a linear furrow or groove can be observed at the limit of the temporal lobe below and the insula, frontal and parietal lobes above.18 Around 15 weeks GA, this groove becomes part of the insular cortex, which is believed to be the first lateral cortical region to develop and is a key region involved in the experience of pain.16 The subplate has also been observed to thin in areas where cortical folding occurs, such as the parieto-occipital sulcus, and in the insula and cingulate gyrus at least from 20 weeks GA.25 It is currently uncertain whether this thinning is due to earlier maturation of these regions, and potentially earlier synaptic activity in the insula and cingulate cortex, which are both key areas in the experience of pain16, or due to incidental morphological changes. Nevertheless, before 26 weeks GA, the foetal brain is largely smooth with only minor evidence of sulcation and gyration. Massive growth of the brain after 34 weeks rapidly results in the characteristic folds and surface features of the more mature brain. By 24 weeks GA, substantial thalamocortical afferents have accumulated at the superficial edge of the subplate, which is the stepping-off point for axons growing towards their final cortical targets.21 Between 24 and 32 weeks there is substantial ingrowth of thalamocortical axons in the cortical plate of the frontal, somatosensory, visual and auditory cortex and formation of the first synapses in the deep cortical plate. Clear evidence of synaptic activity following auditory stimulation has been recorded from around 26 weeks in utero and somatosensory responses have been recorded in premature neonates of 25 weeks GA following a noxious heel lance.26,27 By around 24 weeks GA, therefore, it can be assumed that noxious peripheral events cause a response in the primary sensory cortex indicating the presence of a spinothalamic connection. Long axonal tracts now course from the periphery and through the brain to the cortex. It is generally accepted that the necessary neural structures for pain are in place and are functional by 24 weeks GA.6–10 Thus, it is possible that measures to prevent pain might be appropriate during invasive procedures after 24 weeks GA.
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Further developments Recently, however, it has become clear that the pre- and post-birth environments are very different with potentially important consequences for painful experiences. It is also becoming clear that completion of the major pathways from the periphery to the cortex, at around 24 weeks GA, does not signal the end of cortical development but rather the beginning of a further maturational process. In an extensive and important review, Mellor et al. 28 described evidence suggesting that the foetus never enters a state of wakefulness in utero. This conclusion was based largely on observations of foetal lambs. Rigatto et al. 29, for example, directly observed an unanaesthetised sheep foetus, in utero, through a Plexiglas window, for a total of 5000 h without observing signs of wakefulness such as eyes opening or coordinated movement of the head. Mellor and colleagues suggest several factors explain this lack of wakefulness including the environment of the womb, which is warm, buoyant and cushioned, and the presence of a chemical environment that preserves a continuous sleep-like unconsciousness or sedation. The environment of the womb and the chemical suppression of wakefulness maintain unconsciousness and suppress higher cortical activation in the presence of intrusive external stimulation. The foetal response to hypoxia and asphyxia, for example, is characterised by apnoea, cessation of foetal body movements and a shift to a more quiescent Electroencephalographic (EEG) state indicative of unconsciousness.30,31 A series of studies have also demonstrated that as spinothalamic pathways complete their connections with the cortex, from around 24 weeks GA, they increasingly stimulate intracortical pathways into development, which is the next major phase of neuronal maturation. This phase involves elaboration of dendrites and axons, formation and regression of synaptic connections and selective elimination of cell populations and corresponds to the cortical maturation described by Goldman-Rakic32 in primates and by Chugani33 in humans. McKinstry et al. 34 illustrated the effects of this development using diffusion tensor imaging (DTI) in neonates born at 26 and 35 weeks GA. Neonates born at 26 weeks GA have a cortical cell structure dominated by radially orientated dendrites that inhibit the spread of water parallel to the surface of the brain. Consequently, DTI measures an elongated diffusion of water in the cortex. Neonates born at 35 weeks GA, in contrast, have a cortical cell structure with radially orientated and basal dendrites that inhibit the spread of water in all directions. Consequently, DTI measures a spherical diffusion of water in the cortex. This proliferation of cortical neurons and the overproduction of their arborisation and synaptic contacts begins prenatally, as illustrated by McKinstry et al.34, but continues postnatally, along with synaptic elimination, pruning and programmed cell death.32,33,35,36 The sedation of the foetus in utero, and the further development of the cortex, which only completes after birth, imply that it is only after birth, when the infant awakens and cortical development completes, that pain will be experienced. To put that slightly differently, it is seemingly reasonable, given the immature nature of the foetus and the apparent lack of wakeful activity, to reject the possibility of foetal pain on the grounds of pain being objectively impossible in utero. The meaning of biological immaturity The conclusion that the foetus cannot experience pain at any stage of development has met with considerable resistance.9,11 Opponents point out that the cortex might not be the only neural structure capable of processing pain. Subcortical structures, such as the brainstem, for example, respond to noxious stimulation. Subcortical responses occur in response to needling from 18 weeks GA.36 In addition, anencephalic infants, who typically lack almost the entire cortex, demonstrate a capacity to learn and show evidence of emotion12,37, which supports the possibility of some kind of brainstemmediated pain experience.11 An anencephalic foetus also withdraws from noxious stimulation, demonstrating that withdrawal is mediated at a subcortical level.38 Infants with significant neonatal neurological injury due to a parenchymal brain injury also respond to noxious stimulation with a pattern of biobehavioural and facial reactions similar to infants without brain injury.39 If the foetus is sedated and asleep in the womb then it might be possible to dispense with all arguments based on neurobiology because it is typically assumed that a sleeping organism cannot feel. Mellor et al. 28 propose that the foetus is unconscious based on the presence of powerful sedating
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chemicals in the womb (most notably adenosine), the presence of sleep-like EEG patterns observed in the lamb foetus that enter a more quiescent state during stress, and a lack of movement during stress. Unfortunately, these conditions do not guarantee or dictate a lack of wakefulness. Relaxation and sleep can be broken by noxious stimuli40 and although the EEG activity in the lamb foetus enters a state of relative quiescence during stress (such as caused by umbilical cord occlusion) there are clear indications of large spikes within that quiescence.31 Rather than EEG silence during stress, there is a shift from one EEG pattern to another and we have no direct means of assessing what either pattern means in terms of experience. It is also questionable whether the stress of umbilical cord occlusion is comparable to the nociceptive stress that will occur during surgery. A series of studies with rats have also demonstrated that mammalian foetal behaviour is complex and organised. Foetal behaviour includes temporal rhythmicity, movement synchrony and motor coordination that are related to postnatal grooming, suckling and locomotor behaviour.41–44 The rat foetus responds vigorously to chemical stimulation, such as a lemon infusion, and preconditioning with other chemical stimulation, such as mint, modifies these responses.45 Human foetuses also detect and respond to chemical stimuli46, move away when approached with a scalpel or needle during surgical procedures47 and show evidence of learning in utero.48,49 While these responses might occur during a state of sleep or sedation they are certainly not incompatible with wakefulness. Associating EEG patterns during gestation with sleep-like states is also difficult because there is, in general, no clear cut-off between conscious and unconscious EEG activity.50,51 For the neonate, and presumably the foetus, sleep is accompanied by ongoing background EEG without obvious differences between wake and sleep.52,53 These observations of cortical activity during ‘sleep’ in the neonate raise the question of what ‘sleep’ and ‘wakefulness’ actually mean for the neonate or foetus. A subcortical response to noxious stimulation and lack of uncertainty regarding the nature of foetal consciousness makes a definitive rejection of foetal pain difficult. The difficulty stems not just from a lack of neuroscientific knowledge but also from a lack of substance with regard to the nature of sensory experience. Without a satisfactory or comprehensive approach to the nature of sensory experience, terms such as ‘awake’ or ‘conscious’ or ‘pain’ and so forth take on a somewhat arbitrary character and can be attached to any apparently coherent neural behaviour. Certain patterns of EEG activity might or might not be associated with being awake; certain neuronal activity might or might not be associated with being conscious; and certain areas of the brain might or might not be necessary for pain. There is no means of deciding these issues without an adequate account of the subjective terms in use. Why the definition of pain is critical How we define pain is critical. Defining pain as the response to noxious stimulation might seem sensible until it is realised that such a definition will allow almost anything to be in pain because even rocks respond to violent force by shattering and thermostats respond to high temperatures by changing their internal state. Allowing rocks and thermostats to have a pain response is much too permissive. Furthermore, a definition of pain based on response leads to a tautological understanding of pain. Pain is defined in terms of a stimulus that is deemed to be painful because it elicits the pain response. Put simply: pain is defined as pain.54,55 A definition of pain that includes the content of pain is required to avoid tautology. Definitions of pain that avoid tautology usually include cognition, sensation and affective processes such as that provided by the International Association for the Study of Pain (IASP).56 The IASP have defined pain as ‘‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life.’’ By this definition, pain is no longer regarded as merely a physical sensation of noxious stimulus and disease but is seen as a conscious experience which may be modulated by mental, emotional and sensory mechanisms and includes both sensory and emotional components. The multidimensional emphasis and reference to subjectivity makes it difficult to deny an active cortical role for pain experience. Suppression of cortical activity is widely associated with profound loss of conscious experience.57 For pain to be supported by subcortical structures, therefore, requires that pain be redefined as something less than a multidimensional, subjective experience.
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Those that support the possibility of foetal pain have made attempts to change the IASP definition of pain.58 Those efforts have largely focussed on removing the apparent requirement for language from the definition and resulted in a new note being added to the IASP definition: ‘‘The inability to communicate verbally does not negate the possibility that an individual is experiencing pain and is in need of appropriate pain-relieving treatment.’’ The note clarifies that being unable to talk does not mean a person is unable to experience pain but it does not change the substance of the IASP definition. It is unlikely that the efforts to change the IASP definition were intended to clarify something as obvious as silence not delivering pain relief. Presumably, the intention was to reduce the requirements for pain experience so that pain could be more easily attributed to inherently, rather than temporarily, non-verbal beings such as the foetus. Rather than something multidimensional and subjective, pain is reduced to a physical, raw nature by stripping away the layers of conceptualisation that we associate with language. The challenge is to understand pain as something apprehended rather than comprehended. Pain is something that just is, an experience that is complete but irreducible and immediate: a pure immediacy that cannot be allowed any durability. Conceptual, language-ridden beings such as persons cannot experience sensation as a pure immediacy. Sensory experiences in conceptual beings are propositional. Such beings are not merely in pain but know that they are in pain. Knowing that I am in pain involves concepts – ‘sore’, ‘stabbing’, ‘damage’, ‘threat’ and ‘body’ – that are themselves rooted in general beliefs. For conceptual beings, there is no such thing as a pure pain experience that can be extracted from those general beliefs. Every painful experience will invoke its own set of autobiographical associations and expectations that form both the content and the context of the pain experience. Conceptual beings cannot return to a more innocent, aconceptual state. Perception in conceptual beings is structured by concepts and categories from language and thought and is directed towards what is recognised as threatening or desirable. The perceptual field no longer dictates behaviour or experience because conceptual beings highlight the structurally relevant elements, keeping the correct components together and the incorrect components apart. Perception demands a flow of interpretation that informs and constitutes the experience. Every experience that a conceptual being has will follow and be dependent upon a period of conceptual development. The foetus has no options regarding its behaviour in the presence of noxious stimuli. It cannot, for example, decide it is in his/her best interests to remain still during surgery any more than he/she can launch a protest against an abortion. The foetus must react according to the dictates of its biology in the presence of an eliciting stimulus. Anything further will require a conceptual apparatus that will be provided as language and higher forms of thought and behavioural organisation become possible through development. The suggestion that the foetus can feel an equivalent pain to that of an older, conceptual infant misses or denies the necessary role of development in constructing sensorial experience. Nevertheless, the question remains, what is sensation before conceptual development? Sensation before conceptual development Insisting that only conceptual beings have the apparatus to engage in sensation means denying sensation to all animals and all infants less than approximately 2–3 months of age. Such a position strikes many as implausible.9,12,58,59 As discussed earlier in this article, one possible way to avoid the conclusion that only human beings of a certain advanced age experience sensation is to define sensation as something raw and pure. Animals and the foetus might have a perceptual sensitivity to features of the environment that are entirely contained within nature. What exists in animals and the foetus also exists in conceptual beings but perceptual sensitivity in conceptual beings is taken up into the ambit of consciousness where raw immediacy becomes abstract experience.59 Even in non-verbal, aconceptual, creatures, however, there is more to perceptual sensitivity than merely neural activity.60,61 The visual system endows objects, for example, with colour in the same sense that cows endow grass with the character of food. Grass is food for cows because cows eat grass. If cows did not eat grass then grass would not be food. The existence of grass as a food for cows depends upon the relationship between cows and grass and that relationship cannot be reduced to a neural event because the neural event is only one part of the story.
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Sensory perception might be viewed in the same way. Sensations are not projected into objects, which cannot sense, but sensations arise through a relation with the object. That relationship makes the appearance and existence of the object, as qualities of the object, possible. Colours, for example, inhere in objects only by virtue of their relations with a being perceptually sensitive to colour. In similar fashion, noxious stimuli are painful only by virtue of their contact with a being perceptually sensitive to stimuli in the noxious range. The entire experience is more than just nervous tissue activity even though the physiological or sensory structure of the perceptually sensitive being determines the experienced content of the stimulus. This observation is important because it allows us to potentially say that the foetus feels pain without forcing us to also say that rocks and thermostats feel pain. 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 when nociceptors develop and mature, and there is evidence of behavioural responses to touch.35 Further developments of the nervous system then provide for alterations or elaborations of the pain response; each development potentially provides what some have called an experience of pain relevant to that stage of development.9,58 Conclusions Decisions regarding foetal pain are typically resolved by reference to neuroanatomy. Before the presence of a system capable of detecting noxious events, it is reasonable to deny the possibility of pain in utero. Deciding the minimally necessary neuroanatomy, however, is not straightforward. There is considerable disagreement regarding the contribution of the cortex and the possibility of pain, and other conscious experiences, being supported subcortically. One reason for this disagreement is the lack of precision in defining what is meant by ‘pain’. If pain is defined in terms of a noxious stimulus being detected by a nervous system that can preferentially respond to stimuli in the noxious range then pain can be attributed to the foetus from around 10 weeks GA. However, if pain is defined as an elaborate multidimensional experience that is subjective, then pain can never be attributed to the foetus because it is implausible to attribute that much conceptual activity to the foetus.61 This review is agnostic with regard to which view of pain is ‘correct’. It is possible that both views are correct or both views are incorrect but it is not possible that both views are equivalent. Pain in a conceptual being is both apprehended and comprehended whereas pain in a non-conceptual being is, at most, only apprehended. Once pain is comprehended, there is no return to a more innocent state of apprehension. Sensory experience for conceptual beings is not the product of raw experiences stacked together but is a profoundly different way of experiencing the world. Pain for the foetus, whatever that might feel like, will be bounded by the activity in dedicated neural pathways set in motion by a stimulus in the noxious range. The foetus just is, and his experiences just are, and they just are without further regard. Pain for the conceptual infant, in contrast, will open out into the unfolding of his or her life to be connected with a vast array of other sensations, emotions and understanding of the world and the self. The conceptual being has a self-existence that has great regard towards all experience.
Practice points There are numerous surgical procedures, in addition to surgical abortion, that may induce foetal pain but that remains uncertain. The uncertainty regarding foetal pain means that any direction to change clinical practice based on foetal pain would be premature. The use of analgesia or anaesthetic during in utero procedures should remain at the discretion of the medical team responsible for the procedures.
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Research agenda Clinical trials evaluating the clinical benefit of analgesia or anaesthesia during in utero procedures. Neural development in utero. Psychological investigations of sentient versus propositional sensory experience.
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