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{{Short description|Study of the different types of sensory perception of fetuses during pregnancy}}
{{expert needed|biology|date=August 2009|reason=discrepancy between abortion subsection and rest of the article, and lacking scientific consensus in article overall}}
'''Prenatal perception''' is the study of the extent of [[somatosensory]] and other types of [[perception]] during [[pregnancy]]. In practical terms, this means the study of [[fetus]]es; none of the accepted indicators of perception are present in [[embryo]]s. Studies in the field inform the [[abortion debate]], along with certain related pieces of legislation in countries affected by that debate. As of 2022, there is no [[scientific consensus]] on whether a fetus can feel pain.<ref>{{Cite news |last=Belluck |first=Pam |date=2013-09-17 |title=Complex Science at Issue in Politics of Fetal Pain |language=en-US |work=The New York Times |url=https://www.nytimes.com/2013/09/17/health/complex-science-at-issue-in-politics-of-fetal-pain.html |access-date=2022-09-20 |issn=0362-4331}}</ref><ref>{{Cite web |last=Levitan |first=Dave |date=2015-05-18 |title=Does a Fetus Feel Pain at 20 Weeks? |url=https://www.factcheck.org/2015/05/does-a-fetus-feel-pain-at-20-weeks/ |access-date=2022-09-20 |website=FactCheck.org |language=en-US}}</ref><ref>{{Cite news |last=Karni |first=Annie |date=2022-09-13 |title=Graham Proposes 15-Week Abortion Ban, Splitting Republicans |language=en-US |work=The New York Times |url=https://www.nytimes.com/2022/09/13/us/politics/lindsey-graham-abortion.html |access-date=2022-09-20 |issn=0362-4331}}</ref>
 
==Prenatal hearing==
Numerous studies have found evidence indicating a fetus's ability to respond to auditory stimuli. The earliest fetal response to a sound stimulus has been observed at 16 weeks' gestational age, while the auditory system is fully functional at 25–29 weeks' gestation.<ref>{{cite journal |last1=Graven |first1=Stanley N. |last2=Browne |first2=Joy V. |title=Auditory Development in the Fetus and Infant |journal=Newborn and Infant Nursing Reviews |date=December 2008 |volume=8 |issue=4 |pages=187–193 |doi=10.1053/j.nainr.2008.10.010 |s2cid=6361226 |url=https://www.sciencedirect.com/science/article/pii/S1527336908001347 |access-date=31 May 2022 |language=en |issn=1527-3369}}</ref> At 33–41 weeks' gestation, the fetus is able to distinguish its mother's voice from others.<ref>{{cite journal |doi=10.1016/j.infbeh.2008.10.002 |pmid=19058856 |title=Fetal sensitivity to properties of maternal speech and language |journal=Infant Behavior and Development |volume=32 |issue=1 |pages=59–71 |year=2009 |last1=Kisilevsky |first1=B.S. |last2=Hains |first2=S.M.J. |last3=Brown |first3=C.A. |last4=Lee |first4=C.T. |last5=Cowperthwaite |first5=B. |last6=Stutzman |first6=S.S. |last7=Swansburg |first7=M.L. |last8=Lee |first8=K. |last9=Xie |first9=X. |last10=Huang |first10=H. |last11=Ye |first11=H.-H. |last12=Zhang |first12=K. |last13=Wang |first13=Z. }}</ref><ref>{{cite journal |doi=10.1002/dev.20229 |pmid=17577240 |title=Estimated cardiac vagal tone predicts fetal responses to mother's and stranger's voices |journal=Developmental Psychobiology |volume=49 |issue=5 |pages=543–7 |year=2007 |last1=Smith |first1=Laura S. |last2=Dmochowski |first2=Pawel A. |last3=Muir |first3=Darwin W. |last4=Kisilevsky |first4=Barbara S. }}</ref>
 
==Prenatal pain==
[[File:Pregnancy timeline.png|thumb|400px|right|Pregnancy timeline]]
The hypothesis that human fetuses are capable of perceiving [[pain]] in the first trimester has little support, although fetuses at 814 weeks may respond to touch.<ref>{{Cite journal|last1=Marx|first1=Viola|last2=Nagy|first2=Emese|date=2015-06-08|title=Fetal Behavioural Responses to Maternal Voice and Touch|journal=PLOS ONE|volume=10|issue=6|pages=e0129118|doi=10.1371/journal.pone.0129118|issn=1932-6203|pmc=4460088|pmid=26053388|bibcode=2015PLoSO..1029118M|doi-access=free}}</ref>{{Additional citation needed|date=May 2022|reason=Source is just a single article and not a review; The 8-week figure was only mentioned in passing as a figure from a popular book instead of being an experimental result.}} A multidisciplinary [[systematic review]] from 2005 found limited evidence that thalamocortical pathways begin to function "around 29 to 30 weeks' gestational age", only after which a fetus is capable of feeling pain.<ref name="Lee">{{cite journal|last1=Lee|first1=Susan J.|last2=Ralston|first2=Henry J. Peter|last3=Drey|first3=Eleanor A.|last4=Partridge|first4=John Colin|last5=Rosen|first5=Mark A.|year=2005|title=Fetal Pain|journal=JAMA|volume=294|issue=8|pages=947–54|doi=10.1001/jama.294.8.947|pmid=16118385|doi-access=free}}</ref><ref>{{cite journal |doi=10.1136/bmj.332.7546.909 |pmid=16613970 |pmc=1440624 |title=Can fetuses feel pain? |journal=BMJ |volume=332 |issue=7546 |pages=909–12 |year=2006 |last1=Derbyshire |first1=S. W G }}</ref>
 
In March 2010, the Royal College of Obstetricians and Gynecologists submitted a report,<ref name="royalcollege">{{Cite web|date=March 2010|title=Fetal Awareness – Review of Research and Recommendations for Practice|url=http://www.rcog.org.uk/files/rcog-corp/RCOGFetalAwarenessWPR0610.pdf|url-status=dead|archive-url=https://web.archive.org/web/20111002222748/http://www.rcog.org.uk/files/rcog-corp/RCOGFetalAwarenessWPR0610.pdf|archive-date=2011-10-02|publisher=[[Royal College of Obstetricians and Gynaecologists]]|via=Internet Archive|access-date=2019-03-27}}</ref> 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",<ref name="royalcollege" />{{rp|22}}
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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. A co-author of that report revisited the evidence in 2020, specifically the functionality of the thalamic projections into the cortical [[subplate]], and posited "an immediate and unreflective pain experience...from as early as 12 weeks."<ref>{{Cite journal|last1=Derbyshire|first1=Stuart WG|last2=Bockmann|first2=John C.|date=2020-01-01|title=Reconsidering fetal pain|url=https://jme.bmj.com/content/46/1/3|journal=Journal of Medical Ethics|language=en|volume=46|issue=1|pages=3–6|doi=10.1136/medethics-2019-105701|issn=0306-6800|pmid=31937669|doi-access=free}}</ref>
 
There is a consensus among [[Neural development|developmental neurobiologists]] that the establishment of [[Human thalamus|thalamocortical]] connections (at weeks 22–34, reliably at 29) is a critical event with regard to fetal perception of pain, as they allow peripheral sensory information to arrive at the cortex.<ref>Johnson, Martin and Everitt, Barry. ''[https://books.google.com/books?vid=ISBN0632042877&id=MzZRuSQ5UeEC&pg=PA235&lpg=PA235& Essential reproduction]'' (Blackwell 2000), p. 235. Retrieved 2007-02-21.</ref>
 
Electroencephalography indicates that the capacity for functional pain perception in premature infants does not exist before 29 or 30 weeks; a 2005 meta-analysis states that withdrawal reflexes and changes in heart rates and hormone levels in response to invasive procedures are reflexes that do not indicate fetal pain.<ref name="Lee"/>
 
Several lines of evidence suggest that a fetus does not awaken during its time in the womb. Much of the literature on fetal pain simply extrapolates from findings and research on premature babies. The presence of such chemicals as [[adenosine]], [[pregnanolone]], and [[prostaglandin]]-D<sub>2</sub> in both human and animal fetuses, indicate that the fetus is both [[sedation|sedated]] and [[anesthesia|anesthetized]] when in the womb. These chemicals are oxidized with the newborn's first few breaths and washed out of the tissues, increasing consciousness.<ref>{{Cite journal|last1=Lagercrantz|first1=Hugo|last2=Changeux|first2=Jean-Pierre|date=March 2009|title=The Emergence of Human Consciousness: From Fetal to Neonatal Life|url=http://www.nature.com/doifinder/10.1203/PDR.0b013e3181973b0d|journal=Pediatric Research|volume=65|issue=3|pages=255–260|doi=10.1203/PDR.0b013e3181973b0d|pmid=19092726|s2cid=39391626|issn=0031-3998|quote=The delivery from the mother's womb thus causes arousal from a "resting," sleeping, state in utero. After birth, electrophysiological signs on EEG scalp recordings indicate an intense flow of novel sensory stimuli after birth… In addition, arousal is enhanced by the release from endogenous analgesia possibly caused by removal of the mentioned placental "suppressors" which in utero selectively inhibit neural activity of the fetus…. The catecholamine surge triggered by vaginal delivery may also be critical for the arousal at birth.|doi-access=free}}</ref> If the fetus is asleep throughout gestation then the possibility of fetal pain is greatly minimized,<ref name="Diesch">{{cite journal |doi=10.1016/j.brainresrev.2005.01.006 |pmid=16269314 |title=The importance of 'awareness' for understanding fetal pain |journal=Brain Research Reviews |volume=49 |issue=3 |pages=455–71 |year=2005 |last1=Mellor |first1=David J. |last2=Diesch |first2=Tamara J. |last3=Gunn |first3=Alistair J. |last4=Bennet |first4=Laura |s2cid=9833426 }}</ref><ref>{{cite news|last=Paul|first=AM|title=The First Ache|url=https://www.nytimes.com/2008/02/10/magazine/10Fetal-t.html|newspaper=The New York Times|date=2008-02-10}}</ref> although some studies found that the adenosine levels in third-trimester fetuses are only slightly higher than those in adults' blood.<ref>{{cite journal |doi=10.3109/14767058.2011.632040 |title=Is fetal pain a real evidence? |journal=[[The Journal of Maternal-Fetal & Neonatal Medicine]] |volume=25 |issue=8 |pages=1203–8 |year=2012 |last1=Bellieni |first1=Carlo Valerio |last2=Buonocore |first2=Giuseppe |pmid=22023261 |s2cid=20578842 }}</ref>
 
===Fetal anesthesia===
Direct fetal [[analgesia]] is used in only a minority of prenatal surgeries.<ref>{{cite journal |doi=10.3109/14767058.2012.718392 |title=Use of fetal analgesia during prenatal surgery |journal=The Journal of Maternal-Fetal & Neonatal Medicine |volume=26 |pages=90–5 |year=2012 |last1=Bellieni |first1=Carlo V. |last2=Tei |first2=M. |last3=Stazzoni |first3=G. |last4=Bertrando |first4=S. |last5=Cornacchione |first5=S. |last6=Buonocore |first6=G. |issue=1 |pmid=22881840 |s2cid=46355976 }}</ref>
 
Some caution that unnecessary use of fetal anesthetic may pose potential health risks to the 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.<ref name="Lee"/> Given the maternal risk involved and the lack of evidence of any potential benefit to the fetus, administering fetal anesthesia for abortion is not recommended.<ref>{{Cite journal|last1=Society for Maternal-Fetal Medicine|last2=Society of Family Planning|last3=Norton|first3=Mary E.|last4=Cassidy|first4=Arianna|last5=Ralston|first5=Steven J.|last6=Chatterjee|first6=Debnath|last7=Farmer|first7=Diana|last8=Beasley|first8=Anitra D.|last9=Dragoman|first9=Monica|date=2022-02-01|title=Society for Maternal-Fetal Medicine Consult Series #59: The use of analgesia and anesthesia for maternal-fetal procedures|url=https://www.contraceptionjournal.org/article/S0010-7824(21)00441-8/abstract|journal=Contraception|language=English|volume=106|pages=10–15|doi=10.1016/j.contraception.2021.10.003|issn=0010-7824|pmid=34740602|s2cid=243477250|doi-access=free}}</ref>
 
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.<ref name="paul">{{cite news |last=Paul |first=Annie Murphy |url=https://www.nytimes.com/2008/02/10/magazine/10Fetal-t.html |title=The First Ache |work=New York Times |date=February 10, 2008}}</ref>