A new study found that babies who were bottle-fed were more than twice as likely to develop hypertrophic pyloric stenosis than babies who were breastfed. This condition involves a narrowing (stenosis) of the place where the bottom part of the stomach ends and the first part of the small intestine, the duodenum, begins. It is caused by an enlargement (hypertrophy) of the smooth muscle that surrounds this passageway, the pylorus (from the Greek pyloros or gatekeeper).
As the pylorus gets thicker, food has increasing difficulty emptying from the stomach into the small intestine. This results in babies experiencing what is referred to as “projectile vomiting,” where vomit comes out forcefully and often, sometimes at an arch.
Pyloric stenosis is dangerous and should be examined by a physician right away, as eventually, the baby will become dehydrated, will not gain weight, and will lose vital salts and fluids from its system.
Pyloric stenosis in babies, or infantile hypertrophic pyloric stenosis, most commonly develops 3 to 5 weeks after birth. In the United States, it affects around 3 out of 1,000 newborns; it happens more frequently in Caucasian babies than in babies of other ethnicities, and it is more common among male infants than female infants.
The above study, which was recently published online in the journal Pediatrics of the American Medical Association, examined medical records of 714 babies born between 2003 and 2009 in Washington state. Researchers found that compared to breastfed babies, infants who were bottle-fed had 2.3 times the likelihood of developing hypertrophic pyloric stenosis. The odds were especially higher in babies born to women who were 35 or older. Also, first-born children were less likely to get the condition than children who had been born in subsequent pregnancies.
The Seattle researchers found that there was a decrease in the prevalence of pyloric stenosis between 2003 and 2009 in the population that they studied, which they believed to be connected to increasingly higher breastfeeding rates.
A 2012 study in Denmark found that formula-fed babies were about five times likelier to develop pyloric stenosis than babies who were exclusively breastfed. That study examined data for 70,148 infants, most of whom had been breastfed. Sixty-five required surgery for pyloric stenosis, which is the usual present method of treating the condition. Study authors estimated that breastfed babies had a .05 percent chance of developing pyloric stenosis, while bottle-fed babies had a .31 percent chance.
It is interesting to note that babies in the Danish study were found to have a similar risk for developing pyloric stenosis whether they were both breastfed and bottle-fed, whether they had been formerly breastfed exclusively, or whether they were never breastfed. In addition, the risk for bottle-fed infants was similar regardless of the age at which they were first exposed to formula.
While the causes of pyloric stenosis still remain unclear, authors of the Danish study theorized that because formula is harder for babies to digest due to its higher content of whey and casein proteins, formula is retained in the stomach longer than breast milk. Further, when babies are bottle-fed formula, larger amounts are ingested than when they’re breastfed, especially in the case of male babies, who tend to eat more and grow faster than female babies (researchers theorized that this may explain the higher risk of male infants for developing the condition).
Breast milk may also protect against pyloric stenosis because it contains high levels of vasoactive intestinal peptide, a hormone that helps to regulate contraction and dilation of certain muscles, including smooth muscles in the gastrointestinal tract, and may promote relaxation of the pyloric muscle.
Earlier studies have also linked pyloric stenosis to the use by infants of the antibiotic erythromycin in the first two weeks of life, and use of erythromycin by mothers at the end of pregnancy or during breastfeeding.
In addition to persistent, projectile vomiting, other symptoms of pyloric stenosis include:
- Vomited milk may smell curdled due to stomach acid; but it will not have bile, a yellow or greenish fluid secreted by the liver, which mixes with food once it leaves the stomach
- Baby will be hungry after vomiting
- Baby’s stools are fewer and smaller, since little or no food is moving from the stomach into the intestines
- Baby may be constipated or pass stools with mucus in them
- Baby will urinate less frequently
- Baby will fail to gain weight or may even lose weight
- Baby may be less active than usual, which can be a sign of dehydration
- Baby may develop a sunken “soft spot” on top of the head
- You may be able to see waves on baby’s belly after feedings, which are a sign of more forceful stomach contractions as the stomach tries to empty its contents past the narrowed outlet
If your baby is experiencing any of the above symptoms, talk to your pediatrician right away.
By Lisa Pecos