WASHINGTON, Oct. 21 (Xinhua) -- Infants who were bottle fed were more likely to be at risk of developing hypertrophic pyloric stenosis (HPS), a form of stomach obstruction, than those who were breastfed, U.S. researchers said Monday.
The risk appears to be magnified when mothers are older and have had more than one child, researchers from the Seattle Children's Hospital in the U.S. state of Washington, reported in the U.S. journal JAMA Pediatrics.
HPS typically occurs during an infant's first two months of life and surgery is needed to correct the obstruction, which occurs because of a thickening of the smooth muscle layer of the pylorus, the passage between the stomach and small intestines. Despite its incidence of about two cases in every 1,000 births, its cause remains unknown.
The researchers used birth certificates and discharge data in the U.S. state of Washington to examine births between 2003 and 2009 and found 714 infants were admitted with HPS and had a HPS surgery.
The findings indicated that the incidence of HPS decreased from 14 per 10,000 births in 2003 to 9 per 10,000 births in 2009 while breastfeeding prevalence increased from 80 percent in 2003 to 94 percent in 2009.
The researchers said that about 19.5 percent of infants who developed HPS were bottle fed, compared with 9 percent of babies who were breastfed, and the odds of an infant developing HPS also increased when mothers were 35 years and older and had given birth more than once.
"These data suggest that bottle feeding may play a role in HPS etiology, and further investigations may help to elucidate the mechanisms underlying the observed effect modification by age and parity," the researchers concluded.
In a related editorial, Douglas Barnhart, of the Primary Children's Hospital, Salt Lake City in the U.S. state of Utah, said the findings "bring us a step closer to being able to drop idiopathic from hypertrophic pyloric stenosis."
"While the data seem convincing that bottle feeding increases the risk, the reason is not clear," he said. "Further understanding of the pathogenesis of hypertrophic pyloric stenosis will come from both basic research and more detailed epidemiologic studies."