neonatal nurse premature baby
© Hannah McKay/Reuters
A neonatal nurse caring for a premature baby. The author of the study said the team focused on voice because it was not always possible for parents to hold their babies in intensive care.
Researchers measured pain responses in preterm babies during routine procedures in neonatal unit.

Premature babies appear to feel less pain during medical procedures when they are spoken to by their mothers, researchers have found.

Babies that are born very early often have to spend time in neonatal intensive care units, and may need several painful clinical procedures. The situation can also mean lengthy separation from parents.

Now researchers say they have found the sound of a mother's voice seems to decrease the pain experienced by their baby during medical procedures.

Dr Manuela Filippa, of the University of Geneva and first author of the study, said the research might not only help parents, by highlighting that they can play an important role while their baby is in intensive care, but also benefit the infants.

"We are trying to find non-pharmacological ways to lower the pain in these babies," she said, adding that there was a growing body of evidence that parental contact with preterm babies could be important for a number of reasons, including attachment.

Filippa said the team focused on voice because it was not always possible for parents to hold their babies in intensive care, while voice could be a powerful tool to share emotion.

Mothers' voices were studied in particular because infants would already have heard it in the womb. But Filippa said that did not mean a father's voice could not become as familiar over time.

"We are [also] running studies on fathers' vocal contacts," she said.

Writing in the journal Scientific Reports, Filippa and colleagues at the University of Geneva, Parini hospital in Italy and the University of Valle d'Aosta, report how they examined the pain responses of 20 premature babies in neonatal intensive care to a routine procedure in which the foot is pricked and a few drops of blood collected.

The team looked at the babies' responses to the procedure on three occasions, each of which was randomly assigned to one of three conditions: the mother speaking to her child, the mother singing to her child, and the mother not being present.

For each occasion, the team recorded three measures to gauge the level of pain experienced by the baby - the infant's facial expressions, their heartbeat, and their levels of oxygen, with the former recorded and subsequently examined by researchers unaware of which condition it related to.

The results reveal that the pain levels deemed to be experienced by infants fell, on average, from 4.5 to 3 on a 21-point scale when the mothers were speaking.

"For this specific age, this is an important change," said Filippa.

What's more, the team found the mothers' speaking was associated with a significant rise in levels of the hormone oxytocin in saliva samples taken from the babies.

"Oxytocin is known to be involved in the attachment processes and in the maternal sensitivity. It can also be protective against the effects of pain," said Filippa.

A reduction in pain was less clear when the mothers were singing, a finding Filippa said could reflect the constraints of the structure, words, pitch and melody of songs and lullabies.

The study had a number of limitations, including that the number of babies involved was small. "Of course we need to have more preterm babies involved and also other measures, neurological measures, for pain perception," said Filippa.

But, she added, the results were promising. "The key message is that it is very important to involve parents in the early care of their preterm infants, also in difficult situations like painful procedures, using their voice," she said. "What we know now is that parents can do it and it is beneficial."

Rebeccah Slater, a professor of paediatric neuroscience at the University of Oxford who was not involved in the study, said encouraging parents to support their babies during painful procedures using gentle touch and voice has potential benefits for the parents and babies.

"While the reduction in pain scores caused by maternal voice is relatively small, given the ease of implementation and the lack of associated side-effects - which can be caused by alternative pain-relieving medicines - maternal voice provides a promising strategy to improve comfort in babies when they undergo essential medical procedures," she said.