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WHEN DOES A FETUS FEEL PAIN?

Valeo, Tom

ORIGINAL ARTICLE

In Arkansas and Georgia, doctors are required to tell women seeking abortions that the fetus will feel pain during the procedure. Then they must offer anesthesia. Other states are considering similar legislation and Congress may soon vote on the Unborn Child Pain and Awareness Act, which would require abortion providers in the US to read a statement to women seeking an abortion that a fetus older than 20 weeks “has the physical structures necessary to experience pain.”

Is that assertion true? Doctors readily agree that a fetus at 20 weeks and even earlier will pull away from a pin prick or other “noxious stimulus.” They do not agree, however, that the reaction indicates the fetus is experiencing pain.

According to a study published last summer in the Journal of the American Medical Association (JAMA), a fetus is not capable of experiencing pain until 28 to 30 weeks after conception, when the nerves that carry painful stimuli to the brain have developed. Before that, the fetal reaction to a noxious stimulus is a reflex that does not involve consciousness, they write (JAMA 2005; 294:947-954).

That is why the authors of that study oppose any law that would require doctors to tell women that a fetus can experience pain earlier than 28 weeks.

“Because pain perception probably does not function before the third trimester, discussions of fetal pain for abortions performed before the end of the second trimester should be noncompulsory,” the authors state. “Fetal anesthesia or analgesia should not be recommended or routinely offered for abortion because current experimental techniques provide unknown fetal benefit and may increase risks for the woman.”

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LACK OF CONSENSUS: ‘POOR PUBLIC POLICY’

Arthur Caplan, PhD, Director of the Center for Bioethics, and Chair of the Department of Medical Ethics at the University of Pennsylvania, echoed that conclusion in his testimony on November 1 before a congressional subcommittee examining “pain of the unborn.”

Dr. Caplan argued that because there is no consensus in the scientific community about when a fetus can experience pain, a law requiring doctors to claim that a fetus experiences pain from 20 weeks on “would not only be poor public policy, it would set a terrible precedent for other topics where Congress might choose to mandate disclosures about ‘facts’ for political or even ethical reasons which have no foundation in science or medicine.”

But as with other scientific matters that involve reproductive technologies – and research – the issue of when the fetus feels pain has become highly politicized. The JAMA paper was criticized by the National Right to Life Committee, which issued a news release that pointed out that the lead author of the study, Susan J. Lee, was previously a lawyer for NARAL, which supports the right to abortion, while another author, Eleanor A. Drey, MD, is the Director of an abortion clinic in San Francisco. Ms. Lee is currently a medical student at the University of California-San Francisco.

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PAPER IS BALANCED AND PEER-REVIEWED

But that does not discredit the findings, according to Michael A. Williams, MD, Chair of the AAN Ethics, Law and Humanities Committee and Professor of Neurology at Johns Hopkins Medical School. “JAMA is a peer-reviewed publication, which means the article was sent out to other experts who know the science and the ethics,” he said. “If there had been anything false or far out in this paper, it would have been caught. So it has withstood the peer review process for a scientific paper, and I think we should accept it as a peer-reviewed publication. I think it is a balanced paper.”

Dr. Williams contends the proposed legislation is inappropriate because it requires physicians to make statements that are not supported by scientific evidence. “In the absence of pain pathways, there's not good anatomical or physiological evidence that a fetus at 22 weeks feels pain,” said Dr. Williams. “However, that's the premise behind legislation.”

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The JAMA authors examined more than 2,000 articles for information about fetal pain prior to 30 weeks gestational age. The authors defined pain as the awareness of noxious stimuli, which requires the participation of the “thalamocortical circuitry” of the brain. That pathway, they conclude, does not develop until at least 28 weeks after conception.

“To the best of our understanding of how the experience of pain is processed, the immature fetus doesn't have the neural network, the architecture, to experience pain,” said Mark A. Rosen, MD, Professor and Vice Chair of the Department of Obstetrics, Gynecology and Reproductive Sciences and Director of Perinatal Medicine and Genetics at the University of California-San Francisco, one of the authors of the paper. “Therefore, it seems unlikely that what we consider pain is experienced by the fetus.”

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FETAL PAIN EXPERT DISAGREES WITH STUDY

One expert on fetal pain, however, disagrees. Kanwaljeet S. Anand, MD, Professor of Pediatrics, Anesthesiology, Pharmacology, and Neurobiology at the University of Arkansas, asserts the human fetus can experience pain from at least 20 weeks after conception. The “gate theory” of pain first proposed in 1965 by psychologist Ronald Melzack and anatomist Patrick Wall, he contends, demonstrates that pain signals on their way to the brain produce the perception of pain even before they reach the cerebral cortex (Science 1965; 150:971–979).

The authors of the JAMA paper, Dr. Anand said, “represent pain as a hard-wired system, but it is not a hard-wired system. It's not like a computer switch. The nervous system does not develop that way.”

Neonatal pain structures are not the same as those in an adult, Dr. Anand said. The a-beta fibers, for example, which provide proprioception in the adult, are not involved in adult pain processing.

“Yet, in the neonate and fetus they seem to perform that additional function,” Dr. Anand said. “The structures and mechanisms used for pain processing in early life are unique to each stage of development. One cannot say that because the structures used for pain perception in adults are underdeveloped in the fetus, pain perception is not present.”

In addition, the perception of pain requires more than the participation of the somatosensory cortex in the brain, Dr. Anand contends.

“If you ablate the somatosensory cortex, that does not take away pain,” he said. “And if you stimulate the somatosensory cortex, that does not cause pain. On the other hand, if you ablate certain thalamic nuclei, pain goes away, and if you stimulate places in the thalamus, pain is perceived. Sensory processing in the thalamus develops well before the somatosensory cortex.”

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REVIEW IS INCOMPLETE, EXPERT CONTENDS

The authors of the JAMA article, he said, ignore the fact that pain processing also occurs at the thalamic level. He noted that in their survey of the literature, the authors did not include articles that make such a claim.

“A systematic review should be reproducible, but I couldn't replicate the search they had done,” Dr. Anand said. “Obviously, this is not a systematic review. They've ignored relevant evidence for fetal sensory processing, memory, and learning in utero, which implies conscious perception. I think there is concern that the authors have a certain bias because they did not follow the standard methodology for systematic reviews.”

Dr. Anand, who submitted testimony on fetal pain to the US Department of Justice in 2004 regarding the ban on partial-birth abortions, said he is not morally opposed to abortion.

“I have no opinion in that matter,” he said. “I'm not pro-life; I'm not pro-choice. I'm just a country doctor. I don't belong to any organizations that promote or block abortion.”

His testimony, however, has often been cited by those who support a ban on partial-birth abortion.

Although Dr. Rosen does not believe that the fetus before 28 to 30 weeks can experience what we consider pain, he agrees with Dr. Anand that a fetus even before that stage can be harmed by “noxious stimuli.” A needle prick or an incision can set off a stress response that results in an increase in blood pressure, heart rate, and stress hormones, Dr. Rosen said. The stress reaction of the fetus before 28 weeks may be a reflex comparable to an adult pulling his hand from a flame even before feeling pain, but this reflex still can have harmful effects.

“There's plenty of reason to anesthetize a fetus for surgical procedures that have nothing do with the experience of pain,” Dr. Rosen said. “The goal is to block the stress response, which can be detrimental, and a fetus can have a stress response without experiencing pain.”

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POLITICIZING FETAL PAIN

Dr. Rosen also agrees with Dr. Anand that the question of fetal pain has been highly politicized. “The scientific question about the capacity to experience pain is clearly an independent question from the issue of the right to abortion or anything to do with abortion,” Dr. Rosen said.

Dr. Anand, however, believes abortion forces doctors to confront the possibility that the fetus may experience pain.

“First and foremost, I feel that we must come from position of compassion,” Dr. Anand said. “That compassion also applies to fetuses undergoing an abortion. I can't give a prescription of what should or should not be done when a woman comes in for abortion, but my bias would be to give the fetus the benefit of the doubt regarding the likelihood of pain perception.”

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ARTICLE IN BRIEF

  • ✓ Several months after the publication of a paper in JAMA that asserts that fetuses cannot feel pain before 28 to 30 weeks, there is controversy about its conclusions and political ramifications for setting policy on abortion.
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REFERENCE

• Lee SJ, Ralson HJP, Rosen MA, et al. Fetal pain: a systematic multidisciplinary review of the evidence. JAMA 2005;294:947–954.
    ©2006 American Academy of Neurology