Pain in the Womb

The unborn feel pain.

Up until the late 1980s, surgical procedures with neonates (newborn babies up to 28 days old) were mostly performed without the use of anaesthesia and analgesia (pain relief) largely because of safety concerns, and because it was assumed the neonate was not neurologically sophisticated enough to experience pain. [1] Scientific research has since shown that not only do neonates feel pain, but so can unborn babies in the womb - as early as 15 weeks gestation. Current medical evidence has concluded that from the 15th weeks gestation onward, “the fetus is extremely sensitive to painful stimuli,” making it “necessary to apply adequate analgesia to prevent [fetal] suffering.” [2]

The discovery that neonates can feel pain led to the implementation of pain relief measures for operations on neonates. This in turn led to the suggestion that an anaesthetic and analgesic regimen may also be medically and ethically necessary for unborn babies during fetal surgeries. “Most procedures include a general anaesthetic transferred across the placenta … To our [the authors] knowledge, all clinicians or surgeons working with fetal patients advocate the use of fetal anaesthesia and analgesia as standard practice … There is consensus that the use of fetal anaesthesia and analgesia improves maternal and fetal cardiovascular stability, provides the necessary immobility of the fetus and prevents a dangerous fetal physiologic reaction or “stress response” to the surgery.” [1] 

Neuroscientific arguments for fetal pain

The thinking behind the unborn child not being able to feel pain before 24 weeks is linked to the argument that pain is not possible before the development of the cortex (the outer-layer of the brain which is heavily implicated in the experience of pain) [4], and before the periphery is connected to the cortex through the spinal cord and thalamus (commonly described as the body's 'information relay station', residing in the centre of the brain). [5] Those areas are broadly not apparent before 24 weeks’ gestation - leading many medical bodies and press reports to conclude that pain is not possible before this point. However, there is no consensus here. Studies have shown that patients who should theoretically be unable to experience pain, due to either extensive damage to their cortical regions or a congenial malformation (an innate disease or abnormality, present from birth) concerning these areas, are nevertheless able to experience pain [6] [7]. Of course, a couple studies does not disprove a theory, more research is needed. That is where scientific papers concerning the role of the subplate come in. 

The subplate resides beneath the embryonic precursor of the cerebral cortex, known as the cortical plate. [8] The subplate, which appears around week 12, acts as a temporary waiting room between the cortical plate and the thalamus, housing the neurons waiting to reach their ultimate destination in the cortical plate, which has to mature and develop before the neurons can enter. This process eventually results in connections between the thalamus and the cortical plate, a necessary step for the ultimate developmental goal of a sufficient transportation system within the brain of the unborn child, that will allow for sensory experience (including pain). Research has shown that these connections are at minimum partly preserved from the temporary subplate into the mature cortical plate, into adulthood. The retention of these connections implies that the neurons are evidently functionally similar to those that are necessary for mature sensory experience. 

In summary, the science is never 'settled', as demonstrated in this topic of fetal pain. The cortex may very well be central to pain experience, but "there is now good evidence that thalamic projections into the subplate, which emerge around 12 weeks’ gestation, are functional and equivalent to thalamocortical projections that emerge around 24 weeks’ gestation." [1] Therefore, the current scientific research gives credence to the possibility of fetal pain before the commonly accepted point of 24 weeks.

When preterms weren't given anaesthetics

It used to be the case that preterm infants were not given anaesthetic prior to an operation. In an article in the New York Times on fetal pain, Dr. Kanwaljeet Anand noticed that when the infants returned from the theatre, they were in an obvious distressed state. Their skin was grey, their breathing shallow, their pulses weak. He would spend hours stabilizing their vital signs, increasing their oxygen supply and administering insulin to balance their blood sugar. He discovered that infants undergoing major surgery were receiving only a paralytic to keep them still. And it was common in other jurisdictions too as doctors believed that newborns’ nervous systems were too immature to sense pain. [3] 

As mentioned above, adequate pain relief for even the youngest infants is now considered the standard of care, and the treatment that so concerned Anand two decades ago would be considered a violation of medical ethics if it happened today.

Sources

1. Reconsidering fetal pain
2. Appearance of fetal pain could be associated with maturation of the mesodiencephalic structures
3. NY Times - The First Ache
4. Role of the Prefrontal Cortex in Pain Processing
5. Cleveland Clinic - Thalamus 
6. Preserved emotional awareness of pain in a patient with extensive bilateral damage to the insula, anterior cingulate, and amygdala
7. The “Pain Matrix” in Pain-Free Individuals 
8. Cortical Plate