Between 1870 and 1970, the expert consensus was that newborns don’t register pain because to feel pain, nerves sheathed with myelin were required and neonates didn’t possess enough of them. This inspired surgeons — according to a 1970 report in Pediatrics — to perform all kinds of surgeries including open-heart ones on newborns, without anaesthesia. In later years, researchers began to detect evidence of ‘stress’ — namely, quantities of the hormone cortisol — in infants undergoing circumcision. Slowly the medical fraternity came to agree that stress levels were a proxy for pain. It’s been shown that greater stress in adults translates to them expressing a greater degree of pain. But was this true in newborns too?
Moreover, no one had ever observed what happened in the brains of neonates when they were stressed. A study in Current Biology on November 30 shows that stress leads to an apparent disconnect between babies’ brain activity and their behaviour. That is why, the researchers argue, it is often very hard to gauge the extent of pain a newborn registers from grimaces — the only language neonates speak — and warbles alone.
The researchers enrolled 56 healthy, newborn boys and girls and measured their stress levels based on salivary levels of cortisol and heartbeat patterns, both before and after a clinically necessary heel lance. At the same time, they measured the babies’ pain response using EEG brain activity and facial expression.
The data showed that babies with higher levels of stress showed a bigger brain reaction to the heel lance procedure. However, that heightened activity in the brain didn’t correspond to a change in behaviour.
The findings proffer evidence to treat and care for babies in ways that minimise both pain and stress. “This means that caregivers may underestimate a baby’s pain experience,” said Laura Jones of the University College London and among the main authors of the study, in a press statement. Neonatal doctors and nurses know that pre-term babies sometimes “tune out” and become unresponsive when they are overwhelmed. The management of pain in babies is also critical as it can have consequences later. For example, researchers have documented behaviour suggestive of post-circumcision traumatic stress disorder in six-months-old infants as well as PTSD from neonatal circumcision in middle-aged men. Such early adverse experiences may result in stress disorders and hyperactivity, according to a literature compiled by the Circumcision Reference Library.
