Spitting up is very common in babies, as you probably know if you’re a parent to a little one. And most of the time, it’s not a big problem.

Acid reflux occurs when the contents of the stomach flows back into the esophagus. This is very common in infants and most often happens after a feeding.

Although the exact cause is unknown, there are several factors that can contribute to acid reflux. Here’s what we know.

Immature lower esophageal sphincter

The lower esophageal sphincter (LES) is a ring of muscle at the bottom of baby’s esophagus that opens to allow food into the stomach and closes to keep it there.

This muscle may not be fully matured in your baby, especially if they’re premature. When the LES opens, the contents of the stomach can flow back into the esophagus, causing baby to spit up or vomit. As you can imagine, it can cause discomfort.

This is very common and does not usually cause other symptoms. However, constant regurgitation from acid reflux can sometimes cause damage to the esophageal lining. This is much less common.

If spitting up is accompanied by other symptoms, it may then be called gastroesophageal reflux disease, or GERD.

Short or narrow esophagus

Refluxed stomach contents have a shorter distance to travel if the esophagus is shorter than normal. And if the esophagus is narrower than normal, the lining might more easily become irritated.

Diet

Changing the foods baby eats may help reduce the chances of acid reflux. And if you breastfeed, making changes to your diet might help your baby.

Some studies have shown that reducing intake of milk and eggs may help, though more research is needed to determine how much this affects the condition.

Certain foods may be causing acid reflux, depending on your infant’s age. For example, citrus fruits and tomato products increase acid production in the stomach.

Foods like chocolate, peppermint, and high fat foods can keep the LES open longer, causing the contents of the stomach to reflux.

Gastroparesis (delayed emptying of the stomach)

Gastroparesis is a disorder that causes the stomach to take longer to empty.

The stomach normally contracts to move food down into the small intestine for digestion. However, stomach muscles don’t work properly if there is damage to the vagus nerve because this nerve controls the movement of food from the stomach through the digestive tract.

In gastroparesis, the stomach contents remain in the stomach longer than they’re supposed to, encouraging reflux. It’s rare in healthy infants.

Hiatal hernia

A hiatal hernia is a condition in which part of the stomach sticks through an opening in the diaphragm. A small hiatal hernia doesn’t cause problems, but a larger one can cause acid reflux and heartburn.

Hiatal hernias are very common, especially in people over the age of 50, but they are rare in infants. However, the causes are unknown.

A hiatal hernia in children is usually congenital (present at birth) and may cause gastric acid to reflux from the stomach into the esophagus.

Position while feeding

Positioning — especially during and after feeding — is a frequently overlooked cause of acid reflux in infants.

A horizontal position makes it easier for the stomach contents to reflux into the esophagus. Simply keeping baby in an upright position while you’re feeding them and for 20 to 30 minutes afterward may reduce acid reflux.

Sleep positioners and wedges, however, are not recommended while feeding or sleeping. These padded risers are intended to keep your baby’s head and body in one position, but are not recommended by the Food and Drug Administration due to the risk of sudden infant death syndrome (SIDS)

Angle of His

The angle at which the base of the esophagus joins the stomach is known as the “angle of His.” Differences in this angle may contribute to acid reflux.

This angle most likely affects the ability of the LES to keep the contents of the stomach from refluxing. If the angle is too sharp or too steep, it may make it difficult to keep the stomach contents down.

Overfeeding

Feeding your little one too much at once can cause acid reflux. Feeding your infant too frequently can also cause acid reflux. It’s more common for bottle-fed babies to overfeed than breastfed infants.

An oversupply of food can put too much pressure on the LES, which will cause your infant to spit up. That unnecessary pressure is taken off the LES and reflux decreases when you feed baby less food more often.

However, if your baby spits up often, but is otherwise happy and growing well, you may not need to change your feeding routine at all. Talk with your doctor if you have concerns that you are overfeeding your baby.

Your infant will usually grow out of acid reflux. However, call your child’s doctor immediately if you notice that your child:

While it isn’t easy to determine the exact cause of acid reflux in infants, lifestyle and diet changes may help eliminate some of the factors.

If the acid reflux doesn’t go away with these changes and your baby has other symptoms, a doctor may want to perform tests to rule out a gastrointestinal disorder or other problems with the esophagus.