While seemingly pointless in children and adults, hiccups may play a crucial role in fetal brain development.
What exactly are hiccups? They're a reflex, explains Peter Kahrilas, MD, gastroenterologist at Northwestern University's Feinberg School of Medicine in Chicago. Think of the knee-jerk reaction when a doctor taps your patellar tendon—hiccups are an involuntary response.
Irritation in the esophagus or stomach triggers the brainstem to signal the diaphragm and respiratory muscles, causing them to contract suddenly. This leads to a sharp intake of air, while the epiglottis flips to close the windpipe, producing that classic "hic" sound.
That's the mechanism, but what's the purpose? "For adults, they're just an annoyance—essentially useless," says Dr. Kahrilas. Yet researchers suggest hiccups help fetuses practice breathing in the womb.
A recent study analyzed brain activity in 217 newborns, including 13 during hiccup episodes. It revealed stimulation of three distinct brain wave types in the newborns' cortex.
Prior research shows in utero muscle contractions signal the cortex, helping form a "body map" so infants can later control those muscles. Hiccups might do the same for respiratory muscles.
"We know from animal studies that involuntary contractions help the brain map the body," says lead researcher Lorenzo Fabrizi, PhD, from University College London. "Hiccups could map the respiratory system, enabling voluntary control after birth."
This aligns with biology: Fetuses get oxygen via the placenta in utero, but newborns must breathe independently right away.
Hiccups in the womb could be the training ground for those deep breaths you take today to relax or power through a workout. In adulthood, they're just echoes of that early preparation.
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