Infants who are bottle fed are more likely than breastfed babies to develop a type of stomach obstruction that results in projectile vomiting and won’t get better without surgery, a new study shows.
That risk of developing the obstruction is heightened even further when the infant has an older mother, according to the study published in JAMA Pediatrics.
Researchers still don’t know why some babies develop the obstruction, known as hypertrophic pyloric stenosis, said the study’s lead author, Dr. Jarod McAteer, a surgery research fellow at Seattle Children’s Hospital. This study just pinpoints some of the factors that increase the risk, he added.
What scientists do know is that in certain infants, the one-way valve, or sphincter, that allows partially digested food to progress from the stomach to the small intestine can stop working when the muscle that controls the valve’s opening and closing gets too thick. At that point, the connection between the stomach and the small intestine is essentially blocked.
Babies are at risk only when they are between 3- and 6-weeks- old, McAteer said.
“Usually in the first couple of weeks of life, they are completely normal, healthy babies,” he said. “Then they start vomiting and it progressively gets worse over a period of several days until they can’t hold anything down.”
The only solution is surgery to cut the muscle so it will relax and allow food to pass, McAteer said.
For the new study, McAteer and his colleagues from the University of Washington compared 714 infants who developed hypertrophic pyloric stenosis to 7,140 “control” babies who did not develop the obstruction.
After accounting for other known risk factors for obstruction, such as being male and first born, the researchers determined that bottle feeding also significantly raised the risk. In fact, bottle feeding was twice as common among babies with an obstruction, at 19.5 percent, compared with those in the control group (9.1 percent).
Babies with older mothers were also more likely to develop HPS.
The new study may offer mothers another reason to breastfeed, if they are able to, McAteer said.
Still, he doesn’t want to worry moms who can’t breastfeed.
Among the general population, HPS occurs at a rate of about 1 in 1,000, McAteer said. The rate rises to 10 to 15 per 1,000 births when the mother is older and the baby is bottle fed.
“So it’s still very unlikely,” McAteer said.
There are several theories as to why bottle feeding might increase the risk of HPS, the researchers noted. Most appear to have an impact on how full a baby’s stomach can get: Bottle fed infants can consume more food faster; infant formula in and of itself may slow down stomach emptying; and substances in breast milk may help relax the sphincter and aid in stomach emptying.
The new study does a good job with the data on hand, said Dr. Stephen Shew, an associate professor of pediatric surgery at the University of California, Los Angeles, School of Medicine and the Mattel Children’s Hospital.
Nevertheless, it’s an observational study, which means that it doesn’t prove that bottle feeding causes the obstruction, just that bottle feeding is associated with it.
Researchers first got a hint that bottle feeding might be associated with HPS in the '80s when increasing numbers of women turned from breastfeeding to bottle feeding and the rates of obstruction went up, Shew said.
While there will need to be more studies to clarify the issue, “this study is leading more credence to bottle feeding potentially being a factor,” Shew said.