Electronic fields produced by incubators may affect heart rates in newborn babies, a new study has found.
Published in the British Medical Journal, the study does not cast light on any long-term effects that such a change in newborns' heart rates might have.
The researchers, however, say that this may have implications for babies born prematurely, who may spend several weeks or months in incubators.
During the study, the variability in the heart rate of 43 newborn babies was assessed. None of the tots was critically ill or premature.
The heart rates of 27 babies were assessed over three periods of five minutes each, during which the incubator motor was left running, then switched off, and again left running again.
The researchers also tested whether the noise created by the incubator might be a factor by exposing 16 newborns were exposed to "background noise". They did so by placing a tape beside the baby's head, while the incubator motor was switched off.
The tape recording, which reproduced the sound of the incubator fan, was played for five minutes, paused for five minutes, and then played again for five minutes.
While babies exposed to the tape-recorded noise did not show any difference in their heart rates, those in the incubators showed significant differences.
The heart rate variability fell significantly during the periods when the incubator was switched on.
The authors suggest that the powerful electromagnetic fields created by incubators might have resulted in the alteration of heart rates in the newborns.
They conclude that modifications to the design of incubators could help, but they concede that they have yet to discern what long-term consequences there may be of exposure to electromagnetic fields at such a tender age.
"International recommendations and laws set levels to safeguard the health of workers exposed to electromagnetic fields: newborns should be worthy of similar protection," they say.