Watching a newborn hiccup might make parents anxious but scientists say this involuntary process could be an important part of brain development.
Researchers have found that hiccups – caused by sudden, spontaneous contractions of the diaphragm muscle – trigger electrical activity in the brain which could help babies learn how to regulate their breathing.
Kimberley Whitehead, a research associate at the University College London’s department of Neuroscience, Physiology and Pharmacology, and the study’s lead author, said: “The reasons for why we hiccup are not entirely clear, but there may be a developmental reason, given that foetuses and newborn babies hiccup so frequently.”
Pre-term infants – babies who are born more than three weeks before the due date – are particularly prone to hiccups as they spend approximately 1% of their time – around 15 minutes a day – hiccuping.
Hiccuping can also be observed in the womb – sometimes as early as nine weeks into the pregnancy.
The study, published in the Clinical Neurophysiology, was based on brain scans of 13 pre-term and full-term babies, ranging from 30 to 42 weeks gestational age.
Brain activity was recorded with electrodes attached to the scalp, while hiccuping movements were monitored with sensors on the babies’ torso.
The contractions of the diaphragm muscle from a hiccup corresponded with a pronounced response in the brain’s cortex in the form of three brainwaves, the researchers noted.
They believe the third brainwave may link the “hic” sound of the hiccup with the feeling of the muscle contraction in the diaphragm.
Dr Lorenzo Fabrizi, a senior research fellow at the University College London’s department of Neuroscience, Physiology and Pharmacology, and the study’s senior author, said: “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.
“When we are born, the circuits which process body sensations are not fully developed, so the establishment of such networks is a crucial developmental milestone for newborns.”
Although the cause of hiccups in adults still remains unknown, certain things like stress, excitement or eating and drinking can trigger the muscle contraction.
Ms Whitehead said: “Our findings have prompted us to wonder whether hiccups in adults, which appear to be mainly a nuisance, may in fact by a vestigial reflex, left over from infancy when it had an important function.”