Premature Infants Show Different Pain Responses to Repeated Heel Pricks
Premature babies struggle to adapt to pain that lasts or repeats over time. A study conducted with infants at University College London hospitals explored how repeated heel blood tests affect their pain experience and brain activity. The research included twenty newborns divided into two groups: half were born prematurely, while the other half consisted of babies who were closer to full term either at birth or by the time of testing. The postnatal ages of the two groups were similar, ensuring a fair comparison of pain responses across different developmental stages.
To assess pain, researchers performed heel punctures to obtain a small amount of blood. The procedure was repeated for each baby after an interval ranging from three to eighteen minutes, with most infants receiving a single puncture, while a subset required two punctures to collect the necessary blood volume. The team focused particularly on those situations where two punctures were necessary to complete the sampling.
Pain in newborns can trigger a strong stress response, and it was previously unclear whether this response diminishes with repeated exposure. The study measured neural activity through electroencephalography, monitored heart rate with simple electrical readings, and recorded facial expressions and reflexive movements during each needle insertion. Together, these measures provided a comprehensive view of how an infant experiences pain on both the brain and body levels.
The results showed that, for babies who were born at term or reached term age by the testing time, the brain’s response to the second puncture was notably weaker than after the first one. This attenuation aligned with changes in heart rate and facial reactions, suggesting a true reduction in perceived pain with repetition. In contrast, premature infants did not show this same pattern. Their brain activity, heart rate, and facial responses remained strong across both punctures, indicating a heightened or persistent sensitivity to repeated pain in this younger group.
The findings offer important implications for neonatal care. They imply that pain management strategies may need to be tailored to a baby’s developmental stage. For term babies, repeated mild painful procedures could become less distressing over time, while preterm infants might require more proactive or sustained pain relief during similar medical procedures. Medical teams could use this information to optimize comfort, using the smallest necessary needle exposure and combining pain-relieving measures when the infant’s developmental readiness suggests a diminished tolerance for repeated painful stimuli. This approach could help reduce the immediate stress responses that often accompany such procedures while preserving essential clinical testing for health monitoring.
When interpreting these results, it is important to consider the limits of the study. The sample size was modest, and broader investigations could help determine whether the observed differences hold across different hospitals and populations. Additional research might also explore whether other forms of repeated medical testing produce similar patterns and how long any pain reduction persists after successive exposures. The ongoing goal is to refine neonatal pain management so that even necessary tests are as comfortable as possible for infants at varying stages of development.
In the context of childbirth and newborn treatment, clinicians recognize that pain responses in infants are not simply reflexive. They reflect a complex interplay between brain development, autonomic regulation, and behavioural cues. Ongoing attention to how young patients experience repeated pain will continue to guide safe, compassionate, and evidence-based care across hospitals and care centers .