Washington, Oct 22 (IANS): Infants who are bottle-fed are more likely to develop hypertrophic pyloric stenosis (HPS), a form of stomach obstruction, than those who are breastfed, according to US researchers.

The risk appears to be magnified when mothers are older and have more than one child, researchers from the Seattle Children's Hospital in Washington reported in the journal JAMA Pediatrics, Xinhua reported.

HPS typically occurs during the first two months of an infant's life. Surgery is needed to correct the obstruction, which occurs due to thickening of the smooth muscle layer of the pylorus, the passage between the stomach and small intestines.

The researchers used birth certificates and date of discharge to examine births between 2003 and 2009 and found 714 infants were admitted with HPS and had 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 to 9 percent of babies who were breastfed. The number of infants developing HPS also increased when mothers were aged 35 years or more 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.