Pain

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"One focus for the discussion of the 'problem' of late abortion has been based on the claim that a fetus feels pain. The debate about fetal pain originated with discussion which began in the late 1980s, as a consequence of research which indicated that a fetus is capable of a behavioral response to sensory stimulation. Advances in fetal surgery, which include placing valves into the heart and injecting red blood cells into the liver to prevent anaemia, meant that neonatal surgeons and experts in embryology were becoming more and more concerned about the potential consequences of invasive fetal surgery. This concern was given a major boost when Dr Anand, then of the John Radcliffe Hospital, Oxford, demonstrated that new-born babies (neonates) undergoing surgery did better if they were given anaesthetics of a kind usually used only in adult surgery (until very recently, neonates were not given anaesthetic before surgery). In 1992, the New England Journal ran an editorial calling on clinicians to 'Do the Right Thing' concluding that 'it is our responsibility to treat pain in neonates and infants as effectively as we do in other patients'. Since this time, and extensive discussion has taken place in the pages of medical journals, about the nature of pain, with many eminent scientists concluding that they have much more to learn about this phenomenon. Greater knowledge about the causes of pain can only be beneficial to society, and it is important that clinicians do 'do the right thing' where neonates and infants are concerned. It is however extremely unfortunate that a discussion about best clinical practice for new-born babies has led to a debate, based on the notion that a fetus can feel pain, about the 'problem' of late abortion."

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"Evidence Synthesis Pain perception requires conscious recognition or awareness of a noxious stimulus. Neither withdrawal reflexes nor hormonal stress responses to invasive procedures prove the existence of fetal pain, because they can be elicited by nonpainful stimuli and occur without conscious cortical processing. Fetal awareness of noxious stimuli requires functional thalamocortical connections. Thalamocortical fibers begin appearing between 23 to 30 weeks’ gestational age, while electroencephalography suggests the capacity for functional pain perception in preterm neonates probably does not exist before 29 or 30 weeks. For fetal surgery, women may receive general anesthesia and/or analgesics intended for placental transfer, and parenteral opioids may be administered to the fetus under direct or sonographic visualization. In these circumstances, administration of anesthesia and analgesia serves purposes unrelated to reduction of fetal pain, including inhibition of fetal movement, prevention of fetal hormonal stress responses, and induction of uterine atony. Conclusions Evidence regarding the capacity for fetal pain is limited but indicates that fetal perception of pain is unlikely before the third trimester. Little or no evidence addresses the effectiveness of direct fetal anesthetic or analgesic techniques. Similarly, limited or no data exist on the safety of such techniques for pregnant women in the context of abortion. Anesthetic techniques currently used during fetal surgery are not directly applicable to abortion procedures."

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"Whether the fetus can truly experience pain, at least in some way analogous to how adults emotionally understand pain, has been debated extensively over recent years and is of importance given continuing advances in fetal surgical and diagnostic procedures. This question has considerable implications for the management of invasive fetal procedures, particularly as fetal analgesic and anaesthetic treatment is complex and not without risk for the fetus. Prevention and treatment of pain are basic human rights, regardless of age, and if fetal interventions are to progress, then a greater understanding of nociception and stress responses is required. The timing of the neuroanatomical maturation of the nociceptive system is now well understood, and the final critical cortico-thalamic connections appear to be present by 24–28 weeks of gestation. This suggests that the fetus could potentially be able to feel pain by the third trimester, at least in a rudimentary fashion. This concept is said to be supported by studies which show that nociceptive stimuli elicit physiological stress-like responses in the human fetus in utero. However, physiological processing of a nociceptive stimulus and perceiving a nociceptive stimulus as painful are not the same. There are both a physiological and an emotional or cognitive aspect to pain perception, and indeed a significant element of learning [56]. Certainly, processing can be independent of perception, as is demonstrated during surgery under general anesthesia, for example, where nociceptive stimuli can still elicit subcortically mediated physiological stress responses despite unconsciousness. Thus, to emotionally experience pain, we must be cognitively aware of the stimulus (a cortical process), and this in turn requires that we must be conscious. The key question then is not about the anatomic completion or functionality of nociceptive pathways in utero, but whether the fetus is ever conscious and thus aware. In general, discussion of fetal pain perception tends to treat the fetus as an unborn newborn; i.e., that responses of the newborn represent an adequate surrogate for the fetus. The assumption is thus made that if the newborn (including the preterm newborn) can experience wakefulness (and therefore consciousness), and apparently feels pain, then so too must the age-equivalent fetus. Furthermore, evidence for fetal wakefulness (and again therefore consciousness) has been based on how certain fetal responses “resemble” newborn sleep–wake behaviors, rather than a true determination of fetal wakefulness per se. Given the complexities of studying the fetus, extrapolation from or to the newborn state is understandable. Systematic studies of fetal neurological function suggest, however, that there are major differences in the in utero environment and fetal neural state that make it likely that this assumption is substantially incorrect. This has important implications for our understanding of fetal pain perception. The current review critically evaluates the hypothesis that unlike the newborn, the fetus is actively maintained asleep (and unconscious) throughout gestation and cannot be woken by nociceptive stimuli. The evidence is examined with reference to fetal sleep–wake states, the role of cortico-thalamic gating in cortical arousal during sleep, and the unique contribution that certain inhibitory neuromodulators make in utero to cortical suppression. Finally, we briefly discuss the validity of the hypothesis that suggests that the nociceptive input may have long-lasting deleterious effects regardless of whether the fetus is asleep or not."

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"Twenty-five years ago, when Kanwaljeet Anand was a medical resident in a neonatal intensive care unit, his tiny patients, many of them preterm infants, were often wheeled out of the ward and into an operating room. He soon learned what to expect on their return. The babies came back in terrible shape: their skin was gray, their breathing shallow, their pulses weak. Anand spent hours stabilizing their vital signs, increasing their oxygen supply and administering insulin to balance their blood sugar. “What’s going on in there to make these babies so stressed?” Anand wondered. Breaking with hospital practice, he wrangled permission to follow his patients into the O.R. “That’s when I discovered that the babies were not getting anesthesia,” he recalled recently. Infants undergoing major surgery were receiving only a paralytic to keep them still. Anand’s encounter with this practice occurred at John Radcliffe Hospital in Oxford, England, but it was common almost everywhere. Doctors were convinced that newborns’ nervous systems were too immature to sense pain, and that the dangers of anesthesia exceeded any potential benefits. Anand resolved to find out if this was true. In a series of clinical trials, he demonstrated that operations performed under minimal or no anesthesia produced a “massive stress response” in newborn babies, releasing a flood of fight-or-flight hormones like adrenaline and cortisol. Potent anesthesia, he found, could significantly reduce this reaction. Babies who were put under during an operation had lower stress-hormone levels, more stable breathing and blood-sugar readings and fewer postoperative complications. Anesthesia even made them more likely to survive. Anand showed that when pain relief was provided during and after heart operations on newborns, the mortality rate dropped from around 25 percent to less than 10 percent. These were extraordinary results, and they helped change the way medicine is practiced. Today, adequate pain relief for even the youngest infants is the standard of care, and the treatment that so concerned Anand two decades ago would now be considered a violation of medical ethics. But Anand was not through with making observations. As NICU technology improved, the preterm infants he cared for grew younger and younger — with gestational ages of 24 weeks, 23, 22 — and he noticed that even the most premature babies grimaced when pricked by a needle. “So I said to myself, Could it be that this pain system is developed and functional before the baby is born?”"

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"IF THE NOTION that newborns are incapable of feeling pain was once widespread among doctors, a comparable assumption about fetuses was even more entrenched. Nicholas Fisk is a fetal-medicine specialist and director of the University of Queensland Center for Clinical Research in Australia. For years, he says, “I would be doing a procedure to a fetus, and the mother would ask me, ‘Does my baby feel pain?’ The traditional, knee-jerk reaction was, ‘No, of course not.’” But research in Fisk’s laboratory (then at Imperial College in London) was making him uneasy about that answer. It showed that fetuses as young as 18 weeks react to an invasive procedure with a spike in stress hormones and a shunting of blood flow toward the brain — a strategy, also seen in infants and adults, to protect a vital organ from threat. Then Fisk carried out a study that closely resembled Anand’s pioneering research, using fetuses rather than newborns as his subjects. He selected 45 fetuses that required a potentially painful blood transfusion, giving one-third of them an injection of the potent painkiller fentanyl. As with Anand’s experiments, the results were striking: in fetuses that received the analgesic, the production of stress hormones was halved, and the pattern of blood flow remained normal. Fisk says he believes that his findings provide suggestive evidence of fetal pain — perhaps the best evidence we’ll get. Pain, he notes, is a subjective phenomenon; in adults and older children, doctors measure it by asking patients to describe what they feel. (“On a scale of 0 to 10, how would you rate your current level of pain?”) To be certain that his fetal patients feel pain, Fisk says, “I would need one of them to come up to me at the age of 6 or 7 and say, ‘Excuse me, Doctor, that bloody hurt, what you did to me!’ ” In the absence of such first-person testimony, he concludes, it’s “better to err on the safe side” and assume that the fetus can feel pain starting around 20 to 24 weeks."

- Pain

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"Likewise, the release of stress hormones doesn’t necessarily indicate the experience of pain; stress hormones are also elevated, for example, in the bodies of brain-dead patients during organ harvesting. In order for pain to be felt, he maintains, the pain signal must be able to travel from receptors located all over the body, to the spinal cord, up through the brain’s thalamus and finally into the cerebral cortex. The last leap to the cortex is crucial, because this wrinkly top layer of the brain is believed to be the organ of consciousness, the generator of awareness of ourselves and things not ourselves (like a surgeon’s knife). Before nerve fibers extending from the thalamus have penetrated the cortex — connections that are not made until the beginning of the third trimester — there can be no consciousness and therefore no experience of pain. Sunny Anand reacted strongly, even angrily, to the article’s conclusions. Rosen and his colleagues have “stuck their hands into a hornet’s nest,” Anand said at the time. “This is going to inflame a lot of scientists who are very, very concerned and are far more knowledgeable in this area than the authors appear to be. This is not the last word — definitely not.” Anand acknowledges that the cerebral cortex is not fully developed in the fetus until late in gestation. What is up and running, he points out, is a structure called the subplate zone, which some scientists believe may be capable of processing pain signals. A kind of holding station for developing nerve cells, which eventually melds into the mature brain, the subplate zone becomes operational at about 17 weeks. The fetus’s undeveloped state, in other words, may not preclude it from feeling pain. In fact, its immature physiology may well make it more sensitive to pain, not less: the body’s mechanisms for inhibiting pain and making it more bearable do not become active until after birth."

- Pain

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"Recent research provides a potentially urgent reason to ask this question. It shows that pain may leave a lasting, even lifelong, imprint on the developing nervous system. For adults, pain is usually a passing sensation, to be waited out or medicated away. Infants, and perhaps fetuses, may do something different with pain: some research suggests they take it into their bodies, making it part of their fast-branching neural networks, part of their flesh and blood. Anna Taddio, a pain specialist at the Hospital for Sick Children in Toronto, noticed more than a decade ago that the male infants she treated seemed more sensitive to pain than their female counterparts. This discrepancy, she reasoned, could be due to sex hormones, to anatomical differences — or to a painful event experienced by many boys: circumcision. In a study of 87 baby boys, Taddio found that those who had been circumcised soon after birth reacted more strongly and cried for longer than uncircumcised boys when they received a vaccination shot four to six months later. Among the circumcised boys, those who had received an analgesic cream at the time of the surgery cried less while getting the immunization than those circumcised without pain relief. Taddio concluded that a single painful event could produce effects lasting for months, and perhaps much longer. “When we do something to a baby that is not an expected part of its normal development, especially at a very early stage, we may actually change the way the nervous system is wired,” she says. Early encounters with pain may alter the threshold at which pain is felt later on, making a child hypersensitive to pain — or, alternatively, dangerously indifferent to it. Lasting effects might also include emotional and behavioral problems like anxiety and depression, even learning disabilities (though these findings are far more tentative). Do such long-term effects apply to fetuses? They may well, especially since pain experienced in the womb would be even more anomalous than pain encountered soon after birth. Moreover, the ability to feel pain may not need to be present in order for “noxious stimulation” — like a surgeon’s incision — to do harm to the fetal nervous system. This possibility has led some to venture an early end to the debate over fetal pain. Marc Van de Velde, an anesthesiologist and pain expert at University Hospitals Gasthuisberg in Leuven, Belgium, says: “We know that the fetus experiences a stress reaction, and we know that this stress reaction may have long-term consequences — so we need to treat the reaction as well as we can. Whether or not we call it pain is, to me, irrelevant.”"

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"BUT THE QUESTION of fetal pain is not irrelevant when applied to abortion. On April 4, 2004, Sunny Anand took the stand in a courtroom in Lincoln, Neb., to testify as an expert witness in the case of Carhart v. Ashcroft. This was one of three federal trials held to determine the constitutionality of the ban on a procedure called intact dilation and extraction by doctors and partial-birth abortion by anti-abortion groups. Anand was asked whether a fetus would feel pain during such a procedure. “If the fetus is beyond 20 weeks of gestation, I would assume that there will be pain caused to the fetus,” he said. “And I believe it will be severe and excruciating pain.” After listening to Anand’s testimony and that of doctors opposing the law, Judge Richard G. Kopf declared in his opinion that it was impossible for him to decide whether a “fetus suffers pain as humans suffer pain.” He ruled the law unconstitutional on other grounds. But the ban was ultimately upheld by the U.S. Supreme Court, and Anand’s statements, which he repeated at the two other trials, helped clear the way for legislation aimed specifically at fetal pain. The following month, Sam Brownback, Republican of Kansas, presented to the Senate the Unborn Child Pain Awareness Act, requiring doctors to tell women seeking abortions at 20 weeks or later that their fetuses can feel pain and to offer anesthesia “administered directly to the pain-capable unborn child.” The bill did not pass, but Brownback continues to introduce it each year. Anand’s testimony also inspired efforts at the state level. Over the past two years, similar bills have been introduced in 25 states, and in 5 — Arkansas, Georgia, Louisiana, Minnesota and Oklahoma — they have become law. In addition, state-issued abortion-counseling materials in Alaska, South Dakota and Texas now make mention of fetal pain."

- Pain

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"When it comes to the way adults feel pain, science has borne out the optimistic belief that we are all the same under the skin. As research is now revealing, the same may not be true for fetuses; even Anand calls the fetus “a unique organism.” Exhibiting his flair for the startling but apt expression, Stuart Derbyshire warns against “anthropomorphizing” the fetus, investing it with human qualities it has yet to develop. To do so, he suggests, would subtract some measure of our own humanity. And to concern ourselves only with the welfare of the fetus is to neglect the humanity of the pregnant woman, Mark Rosen notes. When considering whether to provide fetal anesthesia during an abortion, he says, it’s not “erring on the safe side” to endanger a woman’s health in order to prevent fetal pain that may not exist. Indeed, the question remains just how far we would take the notion that the fetus is entitled to protection from pain. Would we be willing, for example, to supply a continuous flow of drugs to a fetus that is found to have a painful medical condition? For that matter, what about the pain of being born? Two years ago, a Swiftian satire of the Unborn Child Pain Awareness Act appeared on the progressive Web site AlterNet.org. Written by Lynn Paltrow, the executive director of the National Advocates for Pregnant Women, it urged the bill’s authors to extend its provisions to those fetuses “subjected to repeated, violent maternal uterine contraction and then forced through the unimaginably narrow vaginal canal.”"

- Pain

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"Following concerns generated by the debate on fetal awareness and, particularly, the controversy around whether the fetus could feel pain, the RCOG published, in October 1997, a working party report. A guiding principle in that report was concern that the fetus should be protected from any potentially harmful or painful procedure but, at the same time, the assessment of the capacity to be harmed should be based on established scientific evidence. A major and important conclusion of the report was that the human fetus did not have the necessary structural integration of the nervous system to experience awareness or pain before 26 weeks of gestation. In addition, the report recommended that those carrying out diagnostic or therapeutic procedures on the fetus in utero at or after 24 weeks should consider the need for fetal analgesia. This guidance was welcomed by the clinical and scientific communities, although, in recent years, the report has from time to time come under criticism in some quarters for being out of date and perhaps not having assessed all the known scientific evidence. This criticism has been most evident in discussing the age of viability (at present taken as 24 weeks of gestation in the UK) and the upper gestational limit in the context of induced abortion. The House of Commons Science and Technology Committee, in its report on Scientific Developments Relating to the Abortion Act 1967 (published in October 2007), made a number of important conclusions and recommendations, including some of direct relevance to this issue: ‘We conclude that, while the evidence suggests that foetuses have physiological reactions to noxious stimuli, it does not indicate that pain is consciously felt, especially not below the current upper gestational limit of abortion. We further conclude that these factors may be relevant to clinical practice but do not appear to be relevant to the question of abortion’. A minority report, however, recorded in the minutes of the Committee on 29 October 2007 said, ‘We are deeply concerned that the RCOG failed to give full information to the House of Commons Select Committee...since 1997 the RCOG has consistently denied that foetuses can feel pain earlier than 26 weeks, without acknowledging that amongst experts in this field there is no consensus. Professor Anand is a world authority in the management of neonatal pain and has put forward a cogent argument suggesting that the RCOG position is based on a number of false or uncertain presuppositions’. In the Government response to the House of Commons report (released November 2007) the Minister of State for Health welcomed the report and its conclusions and recommendations but importantly also indicated that ‘we note the Committee’s findings and are in agreement that the consensus of scientific evidence with regard to fetal pain at gestations below 26 weeks and we will be commissioning the College to review their 1997 working party report into fetal pain which will re-examine the latest evidence, much of which has been considered by the Committee, and any new research currently underway’."

- Pain

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"We begin by considering the scientific evidence for the presence of specific anatomical and physiological connections in the brain that are responsible for signalling noxious events to the central nervous system. Noxious stimuli are those that damage the tissues of the body or threaten to do so, such as surgical incision or physical trauma of the skin. In this context, we define pain as ‘the unpleasant sensory or emotional response to such tissue damage’ and trace the development of those responses through fetal development. We follow the path of the signals produced by tissue damage at sensory detectors in the skin and other organs, through to sensory circuits in the spinal cord, brainstem and thalamus and finally to the cerebral cortex, the site of higher level sensory processing. At each stage, we consider the scientific evidence for functional development and how this evidence may be interpreted. This section includes details derived from over 50 papers identified as relevant. Most were published since the last Working Party report1 but this current report also considers the older material included in the previous report. In addition to understanding the anatomical and physiological connections, it is also important to consider the psychological aspects of pain. Broadly accepted definitions of pain refer to pain as a subjective experience involving cognition, sensation and affective processes. These psychological concepts are inevitably harder to address in a fetus but should not be ignored."

- Pain

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"For the fetus to respond to surgical damage, receptors in the affected tissue, such as skin and muscle, must signal the noxious stimulus or damage to the central nervous system. Nociceptors are sensory nerve terminals found in the skin and internal organs that convert tissue damage into electrical signals. The pattern and strength of these nociceptor signals is the first determining step in generating pain. If nociceptor activity is prevented, such as following local anaesthesia, then pain is blocked. Deep tissue damage, for example, that cuts through nerve bundles causes a brief burst of electrical activity in some of the cut nerve endings known as an injury discharge. The injured tissue, however, is now isolated from the central nervous system and, within a few minutes, the isolated tissue becomes ‘numb’ and pain free. Similarly, rare genetic defects that prevent all nociceptive signals result in a complete inability to sense pain. Anatomical studies of human fetal skin shows the presence of nerve terminals and fibres deep in the skin from 6 weeks of gestational age. These terminals are not nociceptors and are specialised for the processing of non-damaging sensations such as touch, vibration and temperature, rather than pain. From 10 weeks, nerve terminals become more numerous and extend towards the outer surface of the skin. The terminals closer to the surface are likely to be immature nociceptors, necessary for pain experience following tissue damage, but they are not unequivocally present until 17 weeks. In other mammals, newly formed fetal nociceptors are able to signal tissue damage but the intensity of their signals is weaker than in adults. The internal organs develop nerve terminals later than the skin, beginning to appear from 13 weeks and then increasing and spreading with age, so that the pancreas, for example, is innervated by 20 weeks."

- Pain

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"Most pain researchers adopt a definition of pain that emphasises the sensory, cognitive and affective response to a noxious event. This understanding of pain is supported by the International Association of Pain (IASP) which defines 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’.1 By this definition, pain does not have primacy over subjectivity, existing before and in addition to subjectivity, but is experienced through subjectivity. It suggests that pain is a part of knowledge and requires the existence of a conceptual apparatus that can marshal all its dimensions into a coherent experience. Although there is considerable merit in the IASP definition of pain, it does tend towards a view of pain as being a constituent part of higher cognitive function. There is disquiet in denying a rawer, more primitive, form of pain or suffering that the fetus, neonate and many animals might experience.2–4 One possible solution is to recognise that the newborn infant might be said to feel pain, whereas only the older infant can experience that they are in pain and explicitly share their condition with others as an acknowledged fact of being.5 Currently there is no immediately obvious way of resolving these arguments empirically. It is possible, however, to argue that even a raw sense of pain involves more than reflex activity and will, therefore, require the higher regions of the cortex to be connected and functional. The age when this minimum requirement is fulfilled is explored in the rest of this chapter."

- Pain

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"The cortex is required for both the discriminative and emotional aspects of the processing of noxious stimuli and both anatomical and functional studies show that cortical neurons begin to receive input about sensory events in the body and the external environment from 24 weeks. Long axonal tracts now course through the brain to the cortex and evoked responses in the primary sensory cortex indicate the presence of a spinothalamic connection and the ability of somatosensory cortical neurons to generate specific activity in response to tissue damaging stimulation. The primary sensory cortex is an important area in pain processing but it is only one of many areas that are active during pain experience. Other important areas include the secondary somatosensory, the anterior cingulate and the insular cortices. Although we may speculate that these regions will also be functionally active from 24 weeks, similar to primary sensory cortex, there is no evidence for this at the moment. It has been suggested that subcortical regions, including the brainstem, and transient brain structures, including the subplate, organise responses to noxious information at each stage of development and provide for a pain experience complete within itself at each stage. There is, however, no evidence or rationale for subcortical and transient brain regions supporting mature function. Although developing brain circuits often display spontaneous neuronal activity this activity is a fundamental developmental process and not evidence of mature function."

- Pain

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"Vaginal delivery may be considered a stress-inducing event to which most fetuses are subject. Fetuses born vaginally have higher levels of catecholamines, cortisol and endorphins than those born by elective caesarean section. It is unclear whether this stress response is related to the painful stimulus of head compression or to other factors, such as mild hypoxaemia or maternal stress. In normal labour, this evidence of fetal stress would be considered a normal fetal physiological response and the stress is thought to have benefits for fetal survival. The labour-related surge in steroids and catecholamines is an important factor in activating sodium channels and promoting the clearance of lung fluid. Babies born by caesarean section before the onset of labour have an increased incidence of respiratory complications, such as transient tachypnoea of the newborn. In addition, recent data show that elements of the stress response, perhaps noradrenaline or endorphins, have a short-term analgesic effect, so that babies born vaginally have an attenuated physiological and behavioural response to a painful stimulus compared with those born by elective caesarean section. Evidence of endogenous fetal analgesia during vaginal birth, as well as the role of catecholamines in promoting lung fluid reabsorption and the respiratory depressant actions of fetal opiate exposure, all suggest that the current approach to intrapartum analgesia, centred around maternal, rather than fetal, requirements for pain relief, is the correct one. The evidence that stress responses during normal vaginal delivery have benefits cannot, however, be readily extrapolated to stress responses during pregnancy."

- Pain

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"The experience of pain needs cognitive, sensory, and affective components, as well as the necessary anatomical and physiological neural connections. Nociceptors first appear at 10 weeks of gestation in the fetus but they are not sufficient for the experience of pain in themselves. That requires that electrical activity is conducted from the receptors into the spinal cord and to the brain. Fibers to nociceptor terminals in the spinal cord have not been demonstrated before 19 weeks of gestation, although it is known that the fetus withdraws from a needle and may exhibit a stress response from about 18 weeks. At this stage, it is apparent that activity in the spinal cord, brain stem and mid-brain structures are sufficient to generate reflex and humoral responses but not sufficient to support pain awareness. At the same time, completion of the major neural pathways from the periphery to the cortex, at around 24 weeks of gestation, heralds the beginning of further neuronal maturation. The proliferation of cortical neurons and synaptic contacts begins prenatally but continues postnatally. Magnetic imaging techniques have recorded fetal auditory and visual responses from 28 weeks but it has not been possible to record directly when cortical neurons first begin to respond to tissue damaging inputs, although there is evidence of neural activity in primary sensory cortex in premature infants (around 24 weeks). It has been suggested that subcortical regions can organise responses to noxious stimuli and provide for the pain experience complete within itself but there is no evidence (or rationale) that the subcortical and transient brain regions support mature function. Thus, although the cortex can process sensory input from 24 weeks, it does not mean that the fetus is aware of pain. There is sound evidence for claiming the cortex is necessary for pain experience but this is not to say that it is sufficient."

- Pain

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