Prenatal perception

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 fetuses; none of the accepted indicators of perception are present in embryos.

Studies in the field inform the abortion debate, along with certain related pieces of legislation in countries affected by that debate.

Numerous studies have found evidence indicating a fetus's ability to respond to auditory stimuli. Research at Zhejiang University, China indicates that fetuses of 33–41 weeks gestational age can not only hear, but also distinguish their mothers' voices from others. See also a UK study on child's "Hearing and listening in the womb": and UK material on "How babies develop hearing":

The hypothesis that human fetuses are capable of perceiving pain in the first trimester is not supported by science; the scientific consensus is that a fetus "is not capable of feeling pain until the third trimester", which "begins at about 27 weeks of pregnancy".

In March 2010, the Royal College of Obstetricians and Gynecologists submitted a report, 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", pg. 22.

The neural regions and pathways that are responsible for pain experience remain under debate but it is generally accepted that pain from physical trauma requires an intact pathway from the periphery, through the spinal cord, into the thalamus and on to regions of the cerebral cortex including the primary sensory cortex (S1), the insular cortex and the anterior cingulated cortex.3,4 Fetal pain is not possible before these necessary neural pathways and structures (figure 1) have developed. -pg. 3

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.

Researchers from the University of California, San Francisco in the Journal of the American Medical Association concluded in a meta-analysis of data from dozens of medical reports and studies that fetuses are unlikely to feel pain until the third trimester of pregnancy. There is a consensus among developmental neurobiologists that the establishment of 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.

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