Bottle-fed infants of older multiparous women at risk for stomach obstruction

By Megan Brooks

NEW YORK (Reuters Health) - New research provides more evidence that bottle feeding may play a role in hypertrophic pyloric stenosis (HPS) and shows that infants of older and multiparous women may be at greatest risk.

Infantile HPS typically occurs in the first two months of life and surgery is needed to correct it. It's one of the most common reasons for surgery in infants.

The authors, reporting online October 21 in JAMA Pediatrics, are not the first to implicate bottle feeding in infantile HPS. A national Danish cohort study published last year in Pediatrics found that any exposure to bottle feeding was associated with HPS. But the causes for infantile HPS remain unclear.

Dr. Jarod McAteer and colleagues from Seattle Children's Hospital and University of Washington, Seattle, say their aim was to define the nature of the relationship and clinical variables that influence it.

Using hospital discharge records from the state of Washington from 2003 to 2009, they identified 714 cases of confirmed infantile HPS and 7,140 control infants who did not develop HPS.

The incidence of HPS per 10,000 births decreased over the study period, from 14 in 2003 to 9 in 2009. At the same time, breast feeding prevalence rose from 80% in 2003 to 94% in 2009.

Compared with control infants, infants with HPS were more likely to be bottle fed after birth (19.5% vs 9.1%). In multivariate analysis, bottle feeding was independently associated with an increased likelihood of HPS (odds ratio 2.31), even after adjusting for infant gender and maternal smoking.

The association between bottle feeding and HPS was more pronounced in women age 35 and older (OR 6.07) and multiparous women (OR 3.42).

"If one assumes bottle feeding to be a causal factor in the etiology of HPS, then according to population attributable risk calculations in our study, about 11% of HPS cases overall are attributable to bottle feeding," the authors note in their report.

"Among mothers 35 years or older, that figure is 32%, compared with essentially 0% in mothers younger than 20 years. This, along with the greater effect in multiparous women, suggests a possible hormonal role for the effect of feeding practice," they say.

"The take-home for clinicians, on one hand, is that we have one more reason to encourage breastfeeding," Dr. McAteer told Reuters Health by email.

"We also hope some of the hormonal hypotheses we put forth in our discussion may prompt further studies into the development of pyloric stenosis," Dr. McAteer said.

In a related editorial, Dr. Douglas Barnhart of the Primary Children's Hospital in Salt Lake City, Utah, says the observation that the effect of bottle feeding on HPS seems to be more important in older and multiparous women is "novel" and "begs the question of a possible hormonal influence given the known age-dependent differences in estradiol levels."

"Perhaps this hormonal effect makes the infant of the older mother more sensitive to the effects of bottle feeding. An alternative explanation is that the breast milk of younger nulliparous mothers may be more protective than that of older mothers. Older mothers' colostrum may have higher fat content. Interestingly, multiparity has also been associated with increased lipid content. It is still not clear if risk of pyloric stenosis is due to bottle feeding per se or lack of breast feeding."

"While the data seem convincing that bottle feeding increases the risk, the reason is not clear," Dr. Barnhart writes. "The fact that pyloric stenosis is still described as idiopathic despite its incidence of 2 per 1,000 is disappointing."

"McAteer and colleagues bring us a step closer to being able to drop idiopathic from hypertrophic pyloric stenosis," he adds.

In a telephone interview with Reuters Health, Dr. Craig Friesen, Division Director, Gastroenterology at Children's Mercy Hospitals and Clinics in Kansas City, Missouri cautioned that "this is an association study and therefore doesn't prove cause and effect. But given that other studies have found this, there probably is an association and it adds to the reasons to promote breast feeding."

SOURCE: http://bit.ly/1cPMzbP

JAMA Pediatr 2013.