Prenatal perception: Difference between revisions

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>

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]]-D₂ 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>

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>