All babies spit up – in that bubbly, wet-burp way. But forceful vomiting in a newborn is the hallmark symptom of pyloric stenosis. When a baby has pyloric stenosis, the muscle in the lower part of the stomach, called the pylorus, builds up and blocks the flow of food into the small intestine. Babies who can’t keep food down need help quickly to avoid dehydration, weight loss, and other complications.


If your baby has pyloric stenosis, he may have:

  • Signs of dehydration, such as dry mouth, lethargy, and going for six hours without a wet diaper
  • Constant hunger
  • Weight loss
  • Fewer bowel movements or bowel movements that is looser than usual
  • A swollen tummy

After your baby eats, and before he vomits, you may notice wavelike contractions across his upper abdomen as the stomach muscles try to push the food past the pylorus. You may also notice that your baby eagerly starts feeding and then becomes anxious and fretful before vomiting. 

If it turns out that your baby does have pyloric stenosis, she’ll need surgery. The operation, called a pyloromyotomy, involves making a single cut in the pyloric muscle. That’s almost always enough to relax the valve so it behaves normally.

Don’t be surprised by an occasional eruption after the procedure. Most babies who’ve had the surgery vomit forcefully a few more times, and the sight of it so soon can be frightening. It’s nothing to worry about, though.

After the surgery, the pylorus should function normally, showing no sign of its still abnormal size.