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Science, politics and fetal pain

Abortion issue muddies real debate on fetal pain perception

Legislation that would require American physicians to inform women seeking abortions that the fetus will experience pain during the procedure, is helping fuel a raging debate about whether, and if so when, a fetus can feel pain. Anti-abortion activists and legislators have made no secret that they hope the bill, which would apply to women at 22 weeks gestation and beyond, will discourage abortions. However, two top medical journals, the Journal of the American Medical Association (JAMA) and the British Medical Journal (BMJ), have reviewed existing evidence and have both concluded that a fetus cannot feel pain until the third trimester of pregnancy.

The article in JAMA, published in 2005, was immediately criticized by anti-abortion groups and others because two of the article’s authors had done abortion-related work. The editor-in-chief of the journal, Catherine DeAngelis, who is a Roman Catholic and opposes abortion, defended publishing the report, telling the Associated Press “"If there weren't four other authors and this wasn't a peer-reviewed journal, I'd worry ... but I don't". The JAMA report concluded that “evidence regarding the capacity for fetal pain is limited but indicates that fetal perception of pain is unlikely before the third trimester.”

The authors of the JAMA review state that although noxious stimuli can trigger withdrawal and hormonal responses consistent with pain perception, the same responses can be triggered by other non-painful stimuli. Therefore, pain perception “requires conscious recognition or awareness of a noxious stimulus.” The authors, using biological arguments about the development of the nervous system, also suggest “fetal awareness of noxious stimuli requires functional thalamocortical connections,” which do not appear until about the 29th or 30th week of gestation.

Although there is a political and moral component to this particular debate, questions about the nature of pain, pain perception and the mechanism of pain have been ongoing for years. For example, it was once widely believed that infants do not experience pain, a belief now shown to be incorrect. At the same time, allodynia, a condition in which even a gentle touch becomes painful, and congenital insensitivity to pain, or an inability to feel pain under any circumstance including injury, illustrate the bizarre and still-elusive nature of pain.

The BMJ article, published in 2006, came to similar conclusions as the JAMA article. Noting that major neurobiological developments occur at 7, 18 and 26 weeks pregnancy, at which point the system of pain detection and response can be considered functional, is not enough to say that the fetus can feel pain. “The subjective experience of pain cannot be inferred from anatomical developments because these developments do not account for subjectivity and the conscious contents of pain,” wrote Stuart Derbyshire, senior lecturer at the School of Psychology, University of Birmingham and author of the article.

Derbyshire suggests that there are few living creatures that are unresponsive to pain citing a fruit fly larva’s ability to bend and roll away from flame. “Although the larva clearly has a biological apparatus to detect and respond to dangerous stimuli, can it be said to feel pain?” With this question, Derbyshire is making a distinction between nociception, the detection and response to noxious stimuli, and pain, which he says requires some kind of “conscious or mental representation of the pain” to actually be experienced.

In other words, even if the wiring is all there and connected, the programming to understand and interpret pain messages traveling through the hardware does not exist.

Additional research suggests there may be other issues at play beyond fetal development and the psychology of pain perception. Pain perception is recognized in premature infants, some of whom have come out of the womb during the second trimester, yet some studies to show that where a fetus or infant is may also be important. The difference may be the uterine environment. The womb is seen as an environment conducive to sleep states and, until birth, it has been suggested that neural chemicals suppress pain perception in the fetal cortex, even if all the hard wiring is in place. These neurochemicals could be likened to a “sleep cocktail” and are no longer produced at such high levels after birth.

As one can imagine, this debate has all kinds of implications, both in the animal and human world, beyond the question of whether a fetus can feel pain before the third trimester. Unfortunately, the moral and political elements of the debate are muddying what are profound questions about the nature of pain and, in the words of Derbyshire, “may expose women to inappropriate interventions, risks and distress.”

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PublishedReviewed by
May 18, 2006Andrew James, MBChB, FRACP, FRCPC

Susan J. Lee, JD; Henry J. Peter Ralston, MD; Eleanor A. Drey, MD, EdM; John Colin Partridge, MD, MPH; Mark A. Rosen, MD. Fetal Pain: A Systematic Multidisciplinary Review of the Evidence Journal of the American Medical Association. 2005;294:947-954.

Derbyshire, SWG. Can fetuses feel pain? British Medical Journal 2006;332:909-912 (15 April), doi:10.1136/bmj.332.7546.909

David J. Mellor, Tamara J. Diesch, Alistair J. Gunn, Laura Bennet. Review: The importance of awareness for understanding fetal pain. Brain Research Reviews 49 (2005) 455– 471

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