Premature babies: not too hot, not too cold

Research by Dr. Lisa McCarthy, funded by the NCRC, has found that the routine use of heated mattresses as a method to keep pre-term neonates warm after birth is a risk to their health, leading to a change in practice in maternity hospitals worldwide.

Up to recently, the international policy has been to place tiny babies born after less than 31 weeks of gestation in the womb, and weighing less than 1,500 grams, in a protective plastic wrapping to keep them warm, and to follow this by placing the babies on heated mattresses.
It was known that temperature control was key to the survival and long-term health of tiny neonates. Dr. McCarthy set out, as part of a PhD research project, to test the effectiveness of the standard methods used in special care units in maternity hospitals – at home and abroad – to control temperature.

Dr. McCarthy carried out her research with neonates at the National Maternity Hospital Holles Street, (NMH), Holles Street, Dublin, under the supervision of Professor Colm O’Donnell, an NCRC principal investigator and consultant neonatologist, at the NMH.

The normal range of temperature for neonates is between 36.5°C and 37.5°C, and the greater the temperature variation outside these norms the poorer the outcome will be for the baby. “The initial goal was to examine 116 babies”, said Dr McCarthy, “but it was not necessary to reach that number as the results were very conclusive, and therefore, on ethical grounds, the study could be stopped with 72 babies studied.”

At that point, the study showed that 59% of babies placed on heated mattresses were found to be outside the normal temperature range, while the figure was 23% – less than half – for babies not placed on the mattresses.

Babies not placed on the mattresses, therefore, were far more likely to remain inside the normal temperature range, and thus to have better health outcomes.

It was a dramatic and somewhat unexpected finding, as there had been a widespread assumption in neonatal medicine that the heated mattresses were beneficial to pre-term neonates.

The findings were presented by Dr McCarthy at the prestigious American Paediatric Society Meeting, and published in the leading research journal, Paediatrics. The research had an immediate impact at the NMH, where the use of heated mattresses was stopped. Other Irish and international maternity hospitals soon followed this example and also stopped their use of heated mattresses.

The international body that produces the accepted recommendations for paediatric healthcare is the International Liaison Committee on Resuscitation, or ILCOR. Until the publication of Dr McCarthy’s research, this influential body had a ‘neutral’ policy on the use of heated mattresses in neonates; they didn’t support or oppose their use.

However, after the research was published, and the findings were widely accepted, ILCOR changed its recommendation on heated mattresses as they were linked to temperature fluctuations in pre-term neonates, and they were unbeneficial. This meant Dr. McCarthy’s NCRC-funded research had a global impact.

“I have met paediatricians in Australia who are familiar with our research on heated mattresses here at the NMH, and have followed a policy of not using them as a result,” said Dr McCarthy. “That is rewarding as our research is helping save babies’ lives worldwide.”