Today Mail Online reported that hiccups help babies to control their breathing. This follows a study in which 13 newborn babies who were hiccupping had their brain monitored using an EEG (electroencephalogram), which records electrical activity in the brain.
The study was based on the working knowledge that when muscles contract they send feedback signals to the brain. The researchers therefore wondered if involuntary contractions of the diaphragm (the muscle that helps us breathe) in response to hiccups would give feedback to a baby's brain in the same way.
They found that in all 13 babies, contractions of the diaphragm were associated with particular electrical patterns in the brain. The pattern was the same in all babies, regardless of whether they were born prematurely, or at full term. As hiccupping has been observed from as early as 9 weeks of pregnancy, the researchers wonder whether nerve signals coming from the diaphragm could help in the foetus or newborn's brain development.
However, this study does not provide any answers on this. It's not possible to draw any meaning from the observations in this small sample of babies and know whether hiccups have any real significance for brain development, respiratory health or disease.
Where did the story come from?
This study was conducted by researchers from University College London and funded by the Medical Research Council. The study was published in the peer-reviewed scientific journal Clinical Neurophysiology and is available to read online.
Both Sky News and The Times confidently report that "hiccups help a baby learn to breathe". This is arguably an over-assumption. The study actually observed no difference in breathing patterns when the babies were hiccupping compared with when they were not. We also do not know whether the electrical patterns observed in the brain had any real significance for the babies' development, as the researchers did not conduct any long-term follow-up.
What kind of research was this?
This was a cross-sectional study measuring brain activity and breathing in a small sample of babies in a neonatal ward. Studies such as this can give us information about how the body works, but the sample is too small to give conclusive answers or make wider assumptions about how this could be linked with health or disease.
What did the research involve?
EEG (electroencephalogram) was used to monitor the electrical activity in the brains of 217 newborn babies when they were around 1 week old. They observed the EEG patterns associated with quiet or active sleep, movement or wakefulness, regular or irregular breathing, and placed additional leads on the body to monitor signals coming from the diaphragm.
13 babies (6% of the sample) had a bout of hiccups during the 70 to 90 minutes of EEG monitoring. These 13 babies were a mix of premature and full-term infants who had been born between 28 and 41 weeks of pregnancy. Out of these 13 babies, 4 of them needed some breathing support with high-flow oxygen, and 3 of them had some brain problems associated with being premature.
The researchers then looked at the recordings from these 13 babies in more detail.
The reason why EEGs were taken for 217 babies – whether for medical reasons, or purely for the purpose of this study, to monitor response to breathing and hiccups – is not specifically reported.
What were the basic results?
The 13 babies who had hiccups during EEG monitoring were more likely to be awake than the remaining sample who did not have hiccups, with 10 being awake and 3 being in active sleep.
Hiccups made no difference to the babies' breathing patterns, heart rates or blood oxygen levels.
The researchers noticed that contraction of the diaphragm caused a pattern of 3 waves of electrical activity mainly around the front, central and temporal regions of the brain. This pattern seen with hiccups was the same for all babies, regardless of whether they were premature or full term.
How did the researchers interpret the results?
The researchers conclude that "hiccups can be encoded by the brain from as early as 10 weeks prior to the average time of birth [very premature babies]".
This is a novel study that has monitored electrical activity in the newborn brain in response to hiccups. The study shows that involuntary contractions of the diaphragm gives feedback signals to the brain, much the same as other muscle contractions.
The same response was seen in all babies, even in the most premature, born at around 29 weeks of pregnancy. The researchers say that antenatal ultrasound scans have observed hiccups in a foetus from as early as 9 weeks of pregnancy. This supports understanding that diaphragm contraction is one of the earliest motor (movement) activities to develop in a baby.
It is possible that sensory signals coming from the body to the brain may help the developing brain in some way. For example, helping to form connections between nerves. The researchers consider this may be 1 reason why hiccups are more common among babies than adults.
However, this is speculation. The main thing to understand is that this small observational study in 13 babies does not provide any definitive answers. It does not tell us that hiccups are necessary for a baby to learn to regulate their breathing. Nor does it tell us whether hiccups have real significance for brain development, including behaviour, intellect, speech and language, or the likelihood of health or disease. This also does not mean the 13 babies who happened to hiccup during this study were any different from the 204 babies who did not.
Overall the findings are of interest but have no direct implications and parents should not be concerned if their baby hiccups or not.
Find out more about caring for a newborn in the pregnancy and baby guide.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Times online (subscription required), 12 November 2019
Sky News online, 12 November 2019
Mail Online, 12 November 2019
Links to the science
Clinical Neurophysiology. Published online 15 October 2019