Research shows unborn child able to experience pain much earlier than customarily assumed

By Randall K. O’Bannon, Ph.D., NRL Director of Education & Research

Editor’s note. Yesterday we wrote about an intriguing post that appeared in the prestigious Journal of Medical Ethics that challenged the “consensus” that the unborn child cannot experience pain until (at least) the 24th week. Making it even more fascinating is that one of the co-authors is unabashedly ‘pro-choice.’

The following, written last year by Dr. O’Bannon, is the perfect background. He explores the relevant research that demonstrates conclusively that the unborn child can and does experience pain—certainly by the 20th week, but likely much earlier. It is reposted with very minor alterations.


…In their zeal to push these late abortions right up to the point of birth (or after, as the governor of Virginia suggested), these advocates have ignored years of research showing that unborn children aborted in the last half of pregnancy experience pain during those abortions, and quite likely even more excruciating pain than they would once born.

While evidence exists of pain receptors appearing as early as five weeks after conception and the child responding to touch as early as week six, even those who hold out for the development of the whole fetal sensory system – pain receptors, nerve tracts, spinal cord, thalamus, cortex – before pain can be experienced had to grant that all these were in place by the child’s twentieth week of life.

It was on this basis that many states passed the Pain-Capable Unborn Child Protection Act, which effectively protected unborn children who might be aborted after twenty weeks old.

That consensus may be shifting, though. Not by moving the pain threshold later (though there are always some who want to push that all the way to birth, or even later), but by asserting that the latest scientific evidence shows that pain capacity occurs even earlier.

The Physiology of Pain in the Unborn

While there are still some who claim a fully developed cortex (some say full maturation of the prefrontal cortex doesn’t occur until one is 25 years old!) is essential to experience pain, more and more researchers and those who do fetal surgery in the womb are convinced that there is evidence that a functioning brain stem and thalamus are sufficient for pain perception in the unborn.

The thalamus is that part of the brain just above the brain stem which processes and relays sensory information and signals to the cerebral cortex. The fetal brain begins to differentiate into its various parts about four to five weeks after conception and the first signs of the thalamus can be seen as early as six weeks (UK Parliamentary Office of Science and Technology, February 1997). Though further development and differentiation will continue to occur over the coming months, the thalamus begins carrying out its functions in a manner of weeks.

Pain receptors show up as early as seven weeks gestation* around the mouth, spread to the palms of the hands and soles of the feet by 11 weeks, the trunk, arms, and legs by the 15th week, and all remaining skin surfaces by the time the unborn child reaches the 20th gestational week (KJS Anand, et al, NEJM, 1987). Nerve tracts connecting the spinal cord and thalamus are established by that time (Adama van Scheltema, et al, Fetal and Maternal Medicine Review, 2008)

Even for those who want to argue that the pain signal must be processed by the cortex to qualify, there is now evidence that the thalamic and subcortical structures are sufficiently mature, and have the necessary thalamocortical connections, in the words of Harvard anesthesiologist Roland Brusseau, that by the 20th gestational week, “it would appear possible that fetuses could experience something approximating ‘pain’” (Brusseau and Myers, Journal of Emergency Nursing, 2006).

Taken together, this would tell us that, though still developing, the entire neural pathway from pain receptors to the cortex is in place by as early as the 18th week of the baby’s life.

Earlier than 20 weeks

New studies say that while contact with the cortex is a significant milestone, it is not necessarily essential to the ability of the unborn child to experience pain.

Clinical data about human beings with damaged or missing cortexes show that pain perception is not significantly altered by that unfunctioning part. This is not so when it comes to the thalamus, though. The absence or stimulation of the thalamus matters greatly. For example, lesions (tissue damage of some kind) of the cortex, no matter how extensive, were not, in studies, associated with coma. But lesions of the neural network centered around the thalamus and connecting the brainstem, thalamus, and cortex were.

In a 2016 study appearing in the Journal of Pain Research entitled “Appearance of fetal pain could be associated with maturation of the mesodiencephalic structures,” researcher Slobodan Sekulic and colleagues say the following after looking at several proposed fetal pain milestones:

When it comes to the fetus, it has to be taken into account that the developing neural elements may be immature, but they are not inactive; the developing pain system has a signaling function during the maturation of the fetus. This system uses the existing neural structures at that moment. According to this, the perception of pain during development is not related to any determined structures of the CNS [central nervous system], on the contrary, the process of pain perception could be made with any structure satisfying the conditions that perception is the organization, identification and interpretation of sensory information in order to represent and understand the environment.

All these data could lead to the hypothesis that the early rudimentary form of the perception of pain in human species could be achieved only with mesodiencephalic structures during intrauterine development.

So that this revolutionary claim is clear, the “mesodiencephalon” and the “mesodiencephalic structures” the authors are talking about involve that midregion of the forebrain which include the brain stem, the thalamus, and surrounding related structures such as the hypothalamus, the epithalamus, and the subthalamus.

“In intact fetuses,” say the authors, “this structure shows signs of sufficient maturation from the 15th week of gestation.”

Medical Experts Concur

Sekulic’s study is one of the most recent and takes the data further than others. But he is not alone in arguing that thalamic development and other markers argue for the possibility of earlier pain perception in the unborn child.

Roland Brusseau, mentioned earlier, explained why anesthesia is given the child in fetal surgery. In a 2013 article in Clinics in Perinatology, Brusseau noted that “the fetus is capable of mounting a physio-chemical stress response to noxious stimuli as early as 18 weeks gestation.”

Mauricio V. Ramirez, writing in the Colombian Journal of Anesthesiology in 2012, noted that all the receptors, neural connections between the spine, thalamus, and cortex were present (some complete) at a range of 17-20 weeks gestation. Ramirez uses this information to argue for the provision of fetal analgesia/anesthesia “during painful interventions that trigger noxious fetal responses.”

In a 2015 article “Secrets of anesthesia in fetoscopic surgery” in Trends in Anaesthesia and Critical Care, Ayten and Kemal Saracoglu argue that given the sufficiency of the neural network circuitry by 17-20 weeks and stress responses in this time frame, “fetal analgesia should be ensured.”

Critics may see these studies and say that researchers are simply being cautious rather than asserting the certainty of the unborn child’s ability to feel pain at this point. The obvious point is that they see the presence and functioning of these structures and feel these developmental facts provide sufficient ground to be concerned about this possibility – so much so that they are willing to stake their professional reputations on recommendations of fetal anesthesia during surgery on those children in the womb.

Even more painful

Sekulic and his colleagues stress that this earlier possible perception means that the pain is likely to be felt more, not less, intensely.

Bearing in mind the dominant role of the reticular formation of the brain stem, which is marked by a wide divergence of afferent information, a sense of pain transmitted through it is diffuse and can dominate the overall perception of the fetus.

In other words, because the neural network feeds such a lot of information to the brain stem, the pain can be overwhelming for the unborn child, especially given that (as the authors write), “The threshold for tactile stimuli is lower at earlier stages of gestation.”

Furthermore, Sekulic and his research colleagues point out, “The pain inhibition mechanisms are not sufficiently developed during intrauterine development, which is another factor that leads to

increased intensity of pain in the fetus.” Between 30 and 32 weeks, humans develop mechanisms that help us moderate or inhibit the experience of pain.

“As a conclusion” says Sekulic, “it could be proposed that the fetus is exposed to rudimentary painful stimuli starting from the 15th gestation week and that it is extremely sensitive to painful stimuli.”

Sekulic and his research team never speak of abortion directly in the article, but implications are clear. Unborn children, particularly those aborted from the mid-second trimester on, are likely to experience excruciating pain when their lives are being taken.

This is hardly the sort of outcome politicians should fight for, much less celebrate.

Like many other medical authors, KJS Anand speaks in terms of “weeks of gestation.” Gestational age in obstetrics is usually dated not to conception, but to the woman’s last menstrual period, or LMP. If so here, the fetal age would be two weeks less than the gestational age, e.g., 20 weeks gestational age would translate into 18 weeks fetal age. The reader should keep this in mind when seeing authors speak of “gestational weeks” later in the article.