Do unborn children feel pain when they are being aborted? The question has taken center stage in the last decade in the U.S. abortion debate. Defenders of the unborn have actively pursued legislation at the state and national levels attempting to restrict abortion based on the phenomenon of fetal pain. Most of these initiatives are premised on the conclusion that pain awareness begins around 20 weeks gestation.
It is important to understand, however, that the question of whether fetuses can feel pain is not an ethical question but an empirical one. And the scientific literature over the past twenty years has offered no conclusive answer. Several influential studies in prestigious peer-reviewed journals have even argued they cannot feel pain until late in the third trimester, or not at all during the gestation period. Abortion activists routinely use these studies to defend their opposition to fetal pain legislation.
Studies denying pain awareness invariably focus on a single point: fetuses cannot give self-report in the form of language; therefore we cannot know for sure whether the multiple reactions they exhibit towards noxious stimuli are correlated to a conscious awareness of pain, or are more akin to reflex reactions occurring beneath the level of consciousness.
This is true enough. Fetuses cannot tell us through the use of language whether they are in pain. But this is by no means the end of the conversation. Here I hope to demonstrate that although the literature does not definitively settle the empirical question, the data give rise to a strong presumption favoring the conclusion that fetuses can and do feel pain beginning at 20 weeks, and perhaps earlier.
Our ability to perceive pain depends on sufficient development of complex anatomical pathways beginning with sensory receptors in the skin connecting to our spinal cord and carrying signals up to the pain-perceiving regions of the brain (the thalamus and cerebral cortex).
Perception in the skin begins around 7 weeks gestation and spreads to all cutaneous surfaces by week 20. Connections between the skin (the "peripheral system") and the spinal cord begin to develop around the 6th week. The cerebral cortex (the principal pain-perceiving region of the brain) begins to form between the 8th and 10th week;by week 20, it has a full complement of approximately one billion cells. In addition, an important neurochemical called substance P, involved in the transmission and modulation of pain impulses, is found in the fetal spinal cord between 12-16 weeks and in high concentrations in regions of the fetal brain stem.
Studies have demonstrated that fetuses mount a sizable stress response to invasive procedures from early in the second trimester. It has long been known that cells that release "endorphins" (from the words "endogenous + morphine" - i.e., internal pain relievers) are found in the fetal pituitary gland. These endorphin-releasing cells respond to stimulation by a chemical called CRF (corticotropin-releasing factor), which is released at the experience of pain or stress. The endorphins cause an interruption in the pain messages normally sent to the brain (i.e., it suppresses pain). Studies suggest that endorphins are released in response to CRF-stimulation at around 20 weeks gestation.
This is confirmed by multiple studies measuring fetal hormonal stress responses to noxious stimuli. An early study in 1994 found that in response to abdominal needle sticks for blood sampling fetuses at 23 weeks mounted a median increase of 183% in concentrations of the stress hormone cortisol and consequently a 590% increase in endorphin concentrations. A later study published in 2001 found evidence that the fetal stress responses occurred significantly earlier. Fetal endorphin elevations were evident from 18 weeks and cortisol elevations from 20 weeks.
Additionally, studies have found a considerable redistribution of blood flow in response to violations of the fetal trunk from as early as 16 weeks. Such redistribution mechanisms aim at protecting more vital organs such as the brain and heart from anticipated injury. Finally, preterm neonates undergoing heal-sticks for blood testing exhibited a type of sweating response that has been validated as a reliable measure of emotional distress (i.e., pain awareness) in full-term babies.
Other remarkable studies of intra-uterine behavior indicate that fetuses from the second trimester possess sufficient conscious awareness to feel pain. From 20 weeks, they can respond to sound (e.g., they are startled by car horns); by 28 weeks, they can discriminate between sound tones; from early in the third trimester the senses of sight, smell and taste appear to be functioning. Studies indicate that fetuses around 22-23 weeks are developmentally advanced enough to engage in rudimentary learning (i.e., a combination of sense perception and retention of memory). Preterm infants from 23 weeks exhibit facial expressions such as grimaces, opening of the mouth, and even crying in response to noxious stimuli. They withdraw their limbs and clench their fists in the way older infants do at the experience of pain.
Some will argue that behavioral and physiological responses to noxious events do not alone prove that fetuses feel pain. Responses to adverse stimuli such as withdrawing, grimacing, crying, release of stress hormones, increase in blood pressure, are all possible in the absence of conscious experience. Spinal cord injury patients, for example, who experience no sensation below the level of the injury may exhibit in their insensate limbs withdrawal responses to invasive stimuli. Patients in the vegetative state thought to be incapable of consciousness exhibit reflex and withdrawal responses. "Brain-dead" bodies exhibit cardiovascular and hormonal stress responses to unanaesthetized incisions. Patients with a pathology called PBA (pseudobulbar affect) exhibit pathological laughing and crying episodes, which do not correspond to feelings of happiness and sadness. Even sleep-walking adults can exhibit behavioral and hormonal responses to moderate noxious stimuli without waking. So the fact that 20-23 week old fetuses exhibit one or another of these responses does not prove they feel pain. Granted.
But given that second trimester fetuses consistently exhibit all the responses, and given that a confluence of analogous responses in developmentally more mature persons clearly correlates to pain experience, to exclude a conscious awareness of pain as part of their explanation in the fetus is tendentious.
Because of the limitations of fetal self-communication, we cannot conclude with certitude that second and third trimester fetuses experience pain. But as I have shown, there are several things we are certain about and they establish a pretty firm presumption in favor of an affirmative conclusion.
We know that in the second trimester the neuroanatomical connections for pain perception are in place; we know that key neurochemical mechanisms underlying pain transmission are active; we know that noxious stimuli cause stress hormone spikes, hemodynamic changes and sweating responses similar to those of persons whose capacity for pain experience is not questioned (and precisely because they have experienced pain); and we know that fetuses exhibit a set of behavioral responses which if exhibited by persons more developmentally advanced unquestionably would be taken to indicate the experience of pain.
These factors together establish a strong presumption in favor of the conclusion that fetuses can and do experience pain from the second trimester of gestation.