For anxious new parents, a hiccupping baby can be another source of worry.
But it is normal for newborns to hiccup for eight minutes at a time, and scientists now suspect they do it to learn how to control their breathing.
When babies hiccup, researchers have discovered they have two brainwaves likely linked to the feeling in their chest, and a third thought to be a reaction to the ‘hic’ sound occurring together with the contraction.
For anxious new parents, a hiccupping baby can be another source of worry. But it is normal for newborns to hiccup for eight minutes at a time, and scientists now suspect they do it to learn how to control their breathing
Hiccups cause a sudden movement of the diaphragm, so the brainwaves may train babies how to control this muscle.
It is important to learn how to consciously breathe, whether to recover from exercise or take a deep breath in stressful situations.
Researchers from University College London recruited 217 babies for their study, managing to find 13 with persistent hiccups. Using electrodes on their heads, they identified the important brainwaves triggered by each hiccup.
Dr Lorenzo Fabrizi, senior author of the study from UCL, said: ‘I know from personal experience that my wife used to really worry when our baby daughter hiccupped.
‘As an adult, we worry that it is annoying and unnecessary for them, but these findings suggest there may be a purpose.
‘The activity resulting from a hiccup may be helping the baby’s brain to learn how to monitor the breathing muscles so that eventually breathing can be voluntary controlled by moving the diaphragm up and down.’
Babies in the womb begin hiccupping as early as nine weeks into pregnancy, and premature babies can spend 15 minutes a day doing it.
Researchers looked at babies ranging from 30 to 42 weeks old, of whom 10 hiccupped while they were awake and three hiccupped during active ‘wriggly’ sleep.
The study put a sensor on each baby’s abdomen, to record their hiccups, and electrodes on their scalp to monitor their brain activity.
It detected three brainwaves in the infant cortex, with the authors believing the first two show a baby detecting the physical properties of the hiccup, like where in the body the hiccups are coming from.
This is valuable information because a hiccup may provide a baby with what is needed to control breathing.
Inhaling means contracting the diaphragm, like a syringe, to enlarge the chest cavity so its pressure drops and air can come into the body. Exhaling relaxes the diaphragm so the air is forced out.
Kimberley Whitehead, from UCL, the first author of the study published in the journal Clinical Neurophysiology, said: ‘As adults we might wish to control our breathing in order to dive underwater, slow our breathing to calm ourselves if our heart is beating with anxiety or take steady breaths after a run.
‘So my guess would be that as the complexity of our actions and experiences increases, the more it is beneficial to be able to have partial voluntary control over our breathing.’
Adults may continue to hiccup as a hangover from our infant days, or perhaps to help with indigestion by preparing the body to be sick.