A recently published report by the Royal College of Obstetricians and Gynaecologists (RCOG) has suggested that fetuses cannot experience pain before 26 weeks' gestation. This received substantial media attention.[2] However, the report of the Commission of Inquiry into Fetal Sentience (the Rawlinson Report) suggested that pain may be experienced from as early as 5.5 weeks.[3] Predictably, this received far less publicity. In the face of such disparity, who should we believe?

The RCOG report favours 26 weeks, when neural connections between the thalamus and cortex are first established; it is these that are assumed to be necessary for the perception of pain. However, the role of the cortex in this respect may well have been overestimated. A group of researchers from the University of California, Los Angeles, have made the point that:

Decerebrate (anencephalic or hydranencephalic) human newborns with relatively intact brain stems can manifest a surprising repertory of complex behaviours, including distinguishing their mothers from others, consolability, conditioning and associative learning....[4]

In addition, Professor John Lorber of Sheffield University has concluded: 'The cortex is probably responsible for a great deal less than most people imagine'. He inferred that many functions assumed to be cortical were located in primitive deep brain structures.[5]

Finally, another extensive review has concluded: 'Sensation of thirst can be demonstrated to persist despite very severe damage to other parts of the brain, for example decortication'.[6]

Simple reflex responses to stimuli are observed in the fetus as early as five weeks after conception,[7] but even the absence of reflex movement does not mean that pain has not been felt. Considerable evidence suggests that the motor nerves of the reflex arc may develop after their sensory counterparts.[8] Thus, the fetus may feel pain before being able to move.

Furthermore, fetuses exhibit hormonal and metabolic responses to painful stress.[9,10] While this does not constitute proof of pain perception, it is similarly suggestive. Even the absence of a stress response would not be conclusive: the relation between hormone levels and reported levels of pain in adults is highly variable.[11] Neither is recollection of pain necessary to establish perception. Alzheimer's sufferers may not remember painful episodes yet obviously suffer at the time.[12]

In the light of such uncertainty and our growing appreciation of the fetus as a patient in its own right, it seems wiser to give these most vulnerable humans the benefit of the doubt.