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Column originally published Feb 17, 2009

Excessive Vomiting In Young Babies Can Be Due To Pyloric Stenosis

Question: Our baby started vomiting about one month after he was born. At first we thought it was the formula that made him sick. We changed the formula, but it didn’t help. We went to a walk-in clinic; the doctor told us that he probably had the flu bug and told us to give him pedialyte. He seemed to be a bit better, but as soon as we started putting him back on formula, he threw up again. Over time, his vomiting became worse and he couldn’t keep anything down. He was losing weight and he stopped peeing. By the time we got him to the hospital, which was two weeks after he started vomiting, he was severely dehydrated. The nurses and doctors had to poke him many times before they could start an IV. They did more tests and found that he had an obstruction in his stomach. He needed an operation the next day. Please tell your readers that they should not ignore vomiting in a small baby.


Thank you very much for telling me about your experience. I am glad that your son has fully recovered. From what you have described, he must be very sick and seriously dehydrated. As a result, it was difficult for doctors and nurses to start an IV to rehydrate him.

There are many reasons why young babies throw up. Blockage of the stomach is actually quite rare, although it is probably one of the most serious medical conditions. The most common cause of vomiting in newborn babies is reflux. Many adults know about acid reflux: the heartburn as well as bitter taste in the throat are the most common symptoms. Acid reflux happens when stomach acid goes up into the esophagus, the tube that connects the back of the throat to the stomach.

This same reflux happens to almost every newborn baby. Most parents would recognize this as spitting, especially when they burp their babies. Some would spit up more than others, but usually no more than a few mouthfuls of breast milk or formula. The majority of milk stays in the stomach; these babies continue to gain weight and thrive in spite of the spitting. The amount of spitting also tends to get better as the baby gets older, when he can sit up and start taking solid food.

Most of the time, spitting up milk doesn’t upset these babies. This is because they produce very little acid in the stomach. However, a small percentage of babies, for reasons still unclear to us, produce more acid in their little stomach. When reflux occurs, the stomach acid will irritate the esophagus. Any adult who suffers from acid reflux disease would know that it really hurts. Babies are the same: they cry and scream, arch their back and draw up their legs in pain. Acid reflux in young babies can be a serious problem, and sometimes very difficult to manage. Some of them need medicine to reduce acid production in the stomach.

The blockage that your son had is called pyloric stenosis. If you imagine the stomach as a little sack, with an inlet where food goes in, and an outlet where food leaves to go into the intestines. This outlet, called the pylorus, is surrounded by a muscle. For some unknown reason, in a small number of babies, this muscle grows excessively and blocks the outlet of the stomach. As a result, milk cannot pass from the stomach into the intestines.

This blockage develops gradually, usually beginning one to two months after birth. At the beginning, these babies may vomit once or twice a day, because some milk can still get through when the blockage is not complete. However, as the blockage gets worse, less and less milk can get through; the vomiting becomes more frequent and more severe. Very often, parents will notice that the vomiting is very forceful, the milk can shoot across the room from the baby. Doctors often call this projectile vomiting.

At first, doctors can mistakenly conclude that the vomiting is due to a virus infection or milk allergy, both of which can show up the same way. Virus infection usually won’t last more than a few days, often accompanied by some fever or diarrhea. Milk protein allergy can also cause vomiting and presence of blood in the stool. If a child is on cows milk formula, changing to a soy formula can solve the problem.

Because pyloric stenosis is a physical obstruction of the stomach, it does not get better by itself. Surgery is always necessary to relieve the blockage. Many of these babies have been vomiting for days, they can become seriously dehydrated like your son, and their electrolytes are often out of whack. They require IV rehydration and correction of electrolytes before surgery can be performed.

The important lesson for parents of young infants is that although spitting is normal for all babies, repeated vomiting, especially when it is forceful, is not normal. Spitting usually involves a few mouthfuls of milk, mostly at the time of burping. These babies will continue to gain weight and have many soaking diapers as well as good bowel movements, because there is enough milk passing through the intestines. It is definitely abnormal if a baby loses weight, or have less peeing and pooping. These babies need to be assessed by physicians who are familiar with small babies.