If your baby spits up—whether it’s all over you or all over himself—he won’t even be fazed by it. Spit up is completely normal, and it doesn’t cause any discomfort or harm. It’s a result of a weak valve in the esophagus that will strengthen over time. If your baby is expelling fluid from his mouth and seems terribly bothered by it, there’s a good chance he is actually vomiting. When most babies vomit it’s projectile, which is another clear and obvious
difference from spit up. Vomiting is not normal in babies, and it’s usually a sign that he or she has a condition called pyloric stenosis. Most babies that develop the condition will show clear signs before they reach six months of age, and only one in every 500 babies will have it.
The pylorus is the muscle in the lower part of the stomach. In babies with the disorder, this muscle builds up too much and blocks the large intestine so that food is stuck in the belly. In addition to projectile vomiting, your baby might also show symptoms of dehydration such as dry mouth and dry diapers. He or she might also constantly be crying for food but never gain any weight. Belching, wave-like stomach contractions, and a swollen belly are more clear signs of pyloric stenosis, and they’ll be obvious on your delicate newborn.
Your baby’s doctor will be able to determine if it is definitely pyloric stenosis after
ultrasounds and blood tests. If your baby in fact has the disorder, he or she will need surgery to remove the muscle that is blocking the intestines. It’s important that you let your doctor know right away that something is wrong. Though you’re feeding the baby, he or she is not digesting any food, so they might as well be starving. They’ll lose weight rapidly if you don’t address the issue as soon as possible, and the weight loss could seriously hinder the early stages of development. Surgery is safe though, and your baby will be home in a couple of days.
If you see that your baby is vomiting, you need to call your doctor right away. Even if pyloric stenosis is not the cause, your baby is losing valuable nutrients by throwing up food, and these nutrients are essential to development in the earliest stages of life. Vomiting can also quickly lead to dehydration.
Source: Christina Pantell: New Insights into the Pathogenesis of Infantile Pyloric Stenosis. Pediatric Surgery International Volume 25 Issue 12 pp. 1043-1052 2009