The alimentary tract is supposed to be a one-way thoroughfare for food — from top (mouth) to bottom.  Sometimes, however, the valve at the top of the stomach (the lower esophageal sphincter) malfunctions, and the contents of the stomach will splash up in the wrong direction.  This is known as gastroesophageal reflux.  Reflux significant enough to cause symptoms of abdominal or chest discomfort and pain (heartburn), decreased appetite, chronic cough, and other symptoms is known as gastroesophageal reflux disease (GERD).

Reflux is common in babies.  In fact, most babies spit up at least a little bit while others spit up a lot.  It’s not surprising when a newborn infant spits up;  a one-day-old’s stomach is the size of a small marble, able to hold only a little more than a teaspoon (5 ml) of milk.  By day three, a newborn’s stomach can hold nearly one ounce (30 ml) of milk, and by one week of age, the stomach has stretched to nearly the size of a ping-pong ball, able to hold one-and-a-half to two ounces (45-60 ml) of milk.  Mothers who breastfeed for the first time find this information reassuring since the early colostrum is only a mouthful or two for each feeding. (It often takes a good week to produce two ounces of milk for each meal, which amazingly matches a newborn’s stomach capacity. Nature is so smart!)

A baby will spit up milk in excess of his stomach’s capacity.  In addition, the lower esophageal sphincter may not be strong or well developed, leading to more reflux.  These babies will typically spit up right after a feeding when their stomachs are full, especially after lying down for a diaper change.  Babies who spit up a little or a lot, don’t seem bothered by spitting up, and continue to gain weight despite losing what can seem to be a lot of milk are called “happy spitters.”  The situation will improve as the baby gets older; extra burp cloths (and maybe a can of “Scotch Guard” for dad’s tie and for your furniture) are all you need to weather the storm.

Most infants with reflux are happy spitters and their parents need only reassurance.  Some babies, however, aren’t happy when they spit up.  Stomach contents are highly acidic.  The esophagus can become inflamed from reflux and cause a baby to become very fussy, especially during and right after feedings.  Body and leg stiffening with back arching, especially while eating, is commonly seen.  Some babies will even gag and choke when the acidic milk comes back up and hits the back of the throat.  At its worst, babies might have so much difficulty feeding without pain that they don’t gain (and may even lose) sufficient weight.  Different approaches in treating these babies with reflux include keeping them more upright after feeding, thickening their formula with cereal, changing infant formulas, and using medications to neutralize the acidity of the stomach’s acid.

After infancy, the lower esophageal sphincter gets stronger, older babies and toddlers spend more time upright, and GERD becomes less common.  Adults who get heartburn can usually tell you what foods trigger symptoms; caffeinated beverages, rich and creamy desserts and chocolate, and alcohol commonly affect adults the most.  Other risk factors for GERD in teenagers and adults include taking certain medications, obesity, and smoking tobacco.  And let’s not forget all the mothers who suffer from reflux while pregnant!

JAMA Pediatrics has a nice review of GERD on its Patient Page here.