Neonatal perception

Neonatal perception

Neonatal perception is the study of the extent of somatosensory and other perceptual systems during pregnancy. In practical terms, this means the study of fetuses; none of the accepted indicators of perception are present in embryos.


Medical studies and reviews

The hypothesis that human fetuses are capable of perceiving pain has not received sufficient evidence to be proven or disproven; the developmental stage of research and instrumentation is so far insufficient to this task. The issue is considerably complicated by the usual difficulties in perceptual research of unresponsive subjects: "Though techniques such as positron electron tomography scanning might reveal those parts of the brain that respond to a painful stimulus, this does not tell us what the individual is experiencing."[1]

The accepted hypothesis of the means by which pain is perceived states that it requires certain physical structures and operations. These are not formed in fetuses until 30 weeks or more. The consensus of the scientific community at this time is that only fetuses of this age or older are capable of perceiving pain.

Researchers from the University of California, San Francisco in the Journal of the American Medical Association concluded in a meta-analysis of data from dozens of medical reports and studies that fetuses are unlikely to feel pain until the third trimester of pregnancy.[2][3] There is an emerging consensus among developmental neurobiologists that the establishment of thalamocortical connections (at about 26 weeks) is a critical event with regard to fetal perception of pain.[4] Because pain can involve sensory, emotional and cognitive factors, it may be "impossible to know" when painful experiences are perceived, even if it is known when thalamocortical connections are established.[5]

Electroencephalography suggests the capacity for functional pain perception in premature infants probably does not exist before 29 or 30 weeks; this study asserted that withdrawal reflexes and changes in heart rates and hormone levels in response to invasive procedures are reflexes that do not indicate fetal pain.[2]

Also in 2005, Mellor and colleagues reviewed several lines of evidence that suggested a fetus does not awaken during its time in the womb. Mellor notes that much of the literature on fetal pain simply extrapolates from findings and research on premature babies. He questions the value of such data:

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.

He and his team detected the presence of such chemicals as adenosine, pregnanolone, and prostaglandin-D2 in both human and animal fetuses, indicating that the fetus is both sedated and anesthetized in the womb. These chemicals are oxidized with the newborn's first few breaths and washed out of the tissues, allowing consciousness to occur. If the fetus is asleep throughout gestation then the possibility of fetal pain is greatly minimized.[6] “A fetus,” Mellor told the NYTimes, “is not a baby who just hasn’t been born yet.”

There is also discussion among researchers about how pain is perceived over-all. Some researchers believe that because pain can involve sensory, emotional and cognitive factors, pain may not be sensed until after birth.[7]

In 2001, a working group of the Medical Research Council (UK) in the United Kingdom called for more research regarding fetal pain.[8] According to the Daily Telegraph, Eve Johnstone, the chair of that working group "makes a strong case for additional research." Ms. Johnstone told the newspaper, "We ought to study this carefully."[9]

Though many researchers in the area of fetal development agree a fetus is unlikely to feel pain until after the seventh month of pregnancy,[2][3] developmental neurobiologists suspect that the establishment of thalamocortical connections (at about 26 weeks) may be critical to fetal perception of pain.[7]

Fetal pain and abortion

Scientific research generally indicates that the fetus is incapable of feeling pain until at least the 24th week.[citation needed] Many pro-life activists strongly believe in the ability of a fetus to perceive pain, and have introduced legislation in line with this belief. However, fetal pain is not a major legal issue in the debate about abortion, and has not been a deciding factor in any US Supreme Court decision, including the 1973 Roe v. Wade.

Such legislation, if passed would likely affect a very small percentage of abortions, as most are performed before week 20.[citation needed]

Medical objections

Medical objections to fetal pain legislation has been raised on a number of grounds. Some caution that unnecessary use of fetal anesthetic may pose potential health risks to the prospective mother.

In the context of abortion, fetal analgesia would be used solely for beneficence toward the fetus, assuming fetal pain exists. This interest must be considered in concert with maternal safety and fetal effectiveness of any proposed anesthetic or analgesic technique. For instance, general anesthesia increases abortion morbidity and mortality for women and substantially increases the cost of abortion. Although placental transfer of many opioids and sedative-hypnotics has been determined, the maternal dose required for fetal analgesia is unknown, as is the safety for women at such doses. [10]

In any event, anesthesia may be unnecessary, as the fetal brain is awash in naturally occurring chemicals that keep it sedated and anesthetized until birth.[11]

Anesthesia researcher, Laura Myers, has suggested the fetal pain legislation may make abortions harder to obtain; because, abortion clinics lack the equipment and expertise to supply fetal anesthesia. Currently, anesthesia is administered directly to fetuses only while they are undergoing surgery.[12]

United Kingdom

In March 2010, the Royal College of Obstetricians and Gynecologists submitted a report, Fetal Awareness - Review of Research and Recommendations for Practice, concluding that "Current research shows that the sensory structures are not developed or specialized enough to respond to pain in a fetus of less than 24 weeks", pg. 22.

The neural regions and pathways that are responsible for pain experience remain under debate but it is generally accepted that pain from physical trauma requires an intact pathway from the periphery, through the spinal cord, into the thalamus and on to regions of the cerebral cortex including the primary sensory cortex (S1), the insular cortex and the anterior cingulated cortex.3,4 Fetal pain is not possible before these necessary neural pathways and structures (figure 1) have developed. -pg. 3

The report specifically identified the anterior cingulate as the area of the cerebral cortex responsible for pain processing. The anterior cingulate is part of the cerebral cortex, which begins to develop in the fetus at week 26.

In 2006, an opinion piece by Stuart Derbyshire in the British Medical Journal concluded that pain is dependent upon cognitive and emotional developments that occur after birth:

Theories of development assume that the early human mind begins with minimal content and gradually evolves into the rich experience of older children and adults. Although the view of a neonate as a blank slate, or tabula rasa, is generally rejected, it is broadly accepted that psychological processes have content concerning people, objects, and symbols, which lay in the first instance outside the brain. If pain also depends on content derived from outside the brain, then fetal pain cannot be possible, regardless of neural development. [13]

In 1996, physiologist Peter McCullagh spoke on behalf of a pro-life group to the British Parliament. He said, "At what stage of human prenatal development are those anatomical structures subserving the appreciation of pain present and functional? The balance of evidence at the present time indicates that these structures are present and functional before the tenth week of intrauterine life."[14] In response, Wendy Savage Press officer, Doctors for a Woman’s Choice on Abortion, pointed out that the majority of surgical abortions in Britain are already performed under general anesthesia, which also affects the fetus. In a letter to the British Medical Journal,April 1997, she deemed the discussion "unhelpful to women and to the scientific debate."

United States

In the 108th Congress, Senator Sam Brownback introduced a bill called the "Unborn Child Pain Awareness Act" for the stated purpose of "ensur[ing] that women seeking an abortion are fully informed regarding the pain experienced by their unborn child.", which was read twice and referred to committee.[15][16] Subsequently 25 states have examined similar legislation related to fetal pain and/or fetal anesthesia,[17] and in 2010Nebraska banned abortions after 20 weeks on the basis of fetal pain.[18] Eight states, Arkansas, Georgia, Louisiana, Minnesota, Oklahoma, Alaska, South Dakota, and Texas have passed laws which introduced information on fetal pain in their state-issued abortion-counseling literature, which one opponent of these laws, the Guttmacher Institute founded by Planned Parenthood, has called "generally irrelevant" and not in line "with the current medical literature".[19] Dr. Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania, said laws such as these "reduce... the process of informed consent to the reading of a fixed script created and mandated by politicians not doctors."[20]


  1. ^ K. J. S. Anand; Patrick J. McGrath, Bonnie J. Stevens. Pain in neonates. Elsevier Health Sciences. 
  2. ^ a b c Lee SJ, Ralston HJ, Drey EA, Partridge JC, Rosen MA (2005). "Fetal pain: a systematic multidisciplinary review of the evidence". JAMA 294 (8): 947–54. doi:10.1001/jama.294.8.947. PMID 16118385. 
  3. ^ a b AP (24 Aug 05). "Study: Fetus feels no pain until third trimester". MSNBC. 
  4. ^ Johnson, Martin and Everitt, Barry. Essential reproduction (Blackwell 2000), p. 215. Retrieved 2007-02-21.
  5. ^ Johnson, Martin and Everitt, Barry. Essential reproduction (Blackwell 2000): "The multidimensionality of pain perception, involving sensory, emotional, and cognitive factors may in itself be the basis of conscious, painful experience, but it will remain difficult to attribute this to a fetus at any particular developmental age." Retrieved 2007-02-21.
  6. ^ Mellor D.J., Diesch T.J., Gunn A.J., & Bennet L. (2005). The importance of ‘awareness’ for understanding fetal pain. Brain Research Reviews, 49(3), 455-71. Retrieved December 23, 2006.
  7. ^ a b Johnson, Martin and Everitt, Barry. Essential reproduction
  8. ^ Medical Research Council, Fetal Pain - Research Review (2001-08-24). Retrieved 2007-03-10.
  9. ^ Highfield, Roger. "Very premature babies may need pain relieving drugs," The Telegraph (2001-08-27). Retrieved 2007-03-10.
  10. ^ Lee SJ, Ralston HJ, Drey EA, Partridge JC, Rosen MA (2005). "Fetal pain: a systematic multidisciplinary review of the evidence". JAMA 294 (8): 947–954. doi:10.1001/jama.294.8.947. PMID 16118385. 
  11. ^ Mellor D.J., Diesch T.J., Gunn A.J., & Bennet L. (2005). The importance of ‘awareness’ for understanding fetal pain. Brain Research Reviews, 49(3), 455-71. Retrieved December 23, 2006.
  12. ^ Paul, Annie. “The First Ache”, New York Times (2008-02-10).
  13. ^ Derbyshire, S.W.G. (2006). Can fetuses feel pain?. British Medical Journal, 332 (7546), 909-12. Retrieved 2006-12-23. Fetus Cannot Feel Pain, Expert Says", Forbes (2006-04-14). Retrieved via 2008-04-13.
  14. ^ McCullagh, Peter. "Foetal sentience. London: All-Party Parliamentary Pro-Life Group (1996). Dr. McCullagh is a Senior fellow in developmental physiology at the John Curtin School of Medical Research, Australian National University. This report was reprinted in the Catholic Medical Quarterly, XLV11 no 2, November 1996, p6. Retrieved 2007-03-10 via
  15. ^ Unborn Child Pain Awareness Act of 2005, S.2466, 108t Cong., 2nd Sess. (2004)
  16. ^ Weisman, Jonathan. "House to Consider Abortion Anesthesia Bill", Washington Post 2006-12-05. Retrieved 2007-02-06.
  17. ^ Paul, Annie Murphy. "The First Ache," The New York times. February 10, 2008. Accessed April 14, 2008.
  18. ^ Newly Passed 'Fetal Pain' Bill in Nebraska Is a Big Deal
  19. ^ Gold, Rachel Benson and Elizabeth Nash. "State Abortion Counseling Policies and the Fundamental Principles of Informed Consent". Guttmacher Policy Review vol. 10, No. 4. 2007
  20. ^ Caplan, Arthur. "Abortion politics twist facts in fetal pain laws" November 30, 2005

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