Fetuses Called Impervious to Sensation of Pain
By Neil Osterweil, MedPage Today Staff Writer
Reviewed by Rubeen K. Israni, M.D., Fellow, Renal-Electrolyte and
Hypertension Division, University of Pennsylvania School of Medicine
April 14, 2006
Explain to interested patients that the author asserts that fetal neural
circuitry determining pain perception is not fully developed until about 26
weeks of gestation, and that fetuses do not have the developmental capacity
to experience pain, which requires development of conscious understanding.
Be aware that three states -- Arkansas, Georgia, and Minnesota -- mandate
that health care providers tell women that fetuses may be able to feel pain
by 20 weeks of gestational age, an assertion that according to the author is
not supported by medical evidence.
Review
BIRMINGHAM, England, April 14 - Fetuses are physically incapable of feeling
pain until the end of the second trimester, and unlike newborn children have
not developed the processes that would allow them to recognize pain as a
signal of a harmful encounter, a researcher here asserted.
"An absence of pain in the fetus does not resolve the question of whether
abortion is morally acceptable or should be legal," wrote Stuart W.G.
Derbyshire, Ph.D., a senior psychologist at the University of Birmingham, in
the April 15 issue of the BMJ, formerly the British Medical Journal.
"Nevertheless, proposals to inform women seeking abortions of the potential
for pain in fetuses are not supported by evidence."
The states of Arkansas, Georgia, and Minnesota have all enacted legislation
requiring that women seeking an abortion be told that fetuses may feel pain
after 20 weeks of gestation; and 22 other states have similar legislation
pending. A comparable federal law has been proposed.
Yet such laws are based on information of dubious merit, Dr. Derbyshire
asserted.
"Legal or clinical mandates for interventions to prevent such pain are
scientifically unsound and may expose women to inappropriate interventions,
risks, and distress," he wrote.
"Avoiding a discussion of fetal pain with women requesting abortions is not
misguided paternalism, but a sound policy based on good evidence that
fetuses cannot experience pain," he added.
The crux of his argument is that both from a physiologic and developmental
standpoint, fetuses cannot experience pain - in part because the neural
circuitry is not fully connected before 26 weeks' gestation, and in part
because fetuses don't have the developmental capacity to understand that a
provocative stimulus is painful.
"Important neurobiological developments occur at seven, 18, and 26 weeks'
gestation and are the proposed periods for when a fetus can feel pain," he
noted. "Although the developmental changes during these periods are
remarkable, they do not tell us whether the fetus can experience 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."
Dr. Derbyshire likened the pain perception system in the developing fetus to
an alarm system in which the wiring is gradually laid down, but the final
connections are not made until 26 weeks gestation, when neuronal projections
from the thalamus to the cortex have been completed.
The minimum gestational age at which a pain signal may be transmitted from
the periphery is seven weeks, the point at which neural projections from the
spinal cord can reach the thalamus, he said.
Yet the wiring from the thalamus to the cortex is not laid down until about
12 to 16 weeks, and thalamic projections into the cortical plate are not
completed until about 23 weeks. Another two to three weeks are needed before
peripheral free nerve endings and their projection sites in the spinal cord
are fully mature.
"By 26 weeks' gestation, the characteristic layers of the thalamus and
cortex are visible, with obvious similarities to the adult brain, and it has
recently been shown that noxious stimulation can evoke hemodynamic changes
in the somatosensory cortex of premature babies from a gestational age of 25
weeks," he wrote. "Although the system is clearly immature and much
development is still to occur, good evidence exists that the biological
system necessary for pain is intact and functional from around 26 weeks'
gestation."
But even with a fully intact and functional system in place, he argued
further, fetuses have not developed the conscious capacity to understand,
process, or experience pain.
He pointed out that the International Association for the Study of Pain
defines pain as "an unpleasant sensory and emotional experience associated
with actual or potential tissue damage, or described in terms of such
damage," and that "pain is always subjective. Each individual learns the
application of the word through experiences related to injury in early
life."
By this definition then, pain is a conscious, learned response, Dr.
Derbyshire said.
"The limited neural system of fetuses cannot support such cognitive,
affective, and evaluative experiences; and the limited opportunity for this
content to have been introduced also means that it is not possible for a
fetus to experience pain," he wrote.
He acknowledged that his thesis is provocative and has both clinical and
public policy implications.
For example, with the growing frequency of in utero surgeries and other
intervention to correct fetal developmental defects, clinicians might be
inclined to give anesthesia to the fetus in the belief that it can mitigate
pain.
"However, the greater immaturity of fetuses and their different hormonal and
physical environment indicate that clinical trials should be carried out
with fetal patients to show improved outcomes," Dr. Derbyshire wrote.
"Currently no defined evidence-based fetal anesthesia or analgesia protocol
exists for these procedures."
And from a political viewpoint, he noted that "the case against fetal pain,
as documented here, indicates that a mandate to provide pain relief before
abortion is not supported by what is known about the neurodevelopment of
systems that support pain."
"Proposals to directly inject fetuses with fentanyl or to provide pain
relief through increased administration of fentanyl or diazepam to pregnant
women, which increase risks to the women and costs to the health provider,
undermine the interests of the women and are unnecessary for fetuses, who
have not yet reached a developmental stage that would support the conscious
experience of pain," Dr. Derbyshire wrote.
Primary source: BMJ
Source reference:
Derbyshire SWG. "Can fetuses feel pain?" BMJ 2006;332:909-12
Leanne Wynne
Midwife in charge of "Women's Business"
Mildura Aboriginal Health Service Mob 0418 371862
--
This mailing list is sponsored by ACE Graphics.
Visit <http://www.acegraphics.com.au> to subscribe or unsubscribe.
