Published: Oct 21, 2013 | Updated: Oct 22, 2013
By Cole Petrochko, Staff Writer, MedPage Today

Full Story:  http://www.medpagetoday.com/Gastroenterology/GeneralGastroenterology/42398

Infants who were bottle fed by older mothers were significantly more likely to be at risk for hypertrophic pyloric stenosis than those who were breastfed, researchers found.

Compared with breastfed infants, bottle-fed infants had an overall 2.31-fold odds of hypertrophic pyloric stenosis (95% CI 1.81-2.95). The problem was significantly more common among children of mothers ages 35 or older (OR 6.07, 95% CI 2.81-13.10) compared with those of mothers 20 or younger (OR 0.98, 95% CI 0.51-1.88), according to Jarod McAteer, MD, MPH, of Seattle Children’s Hospital in Washington, and colleagues.

In addition, the prevalence of hypertrophic pyloric stenosis decreased over time, from 14 per 10,000 births in 2003 to 9 per 10,000 births in 2009, in tandem with increases in breastfeeding prevalence — from 80% in 2003 to 94% in 2009, they wrote online inJAMA Pediatrics.

Other research has shown that hypertrophic pyloric stenosis may have roots in a baby’s low cholesterol levels. The condition, which mostly occurs in infants, can be treated withlaparoscopic surgery or open pyloromyotomy.

The authors conducted a population-based, case-control study of births in 714 infants admitted to the hospital for hypertrophic pyloric stenosis and who received pyloromyotomy; they examined the associations between admission for the disorder and breast versus bottle feeding. Associations were also measured with other potential risk factors, including infant sex, maternal age, maternal race, maternal parity, maternal body mass index, gestational age, birth weight, and maternal smoking status during pregnancy.

Participants were all singleton births who did not present with hypertrophic pyloric stenosis at birth, and who did not have another diagnosis of major congenital gastrointestinal anomalies.

Controls were randomly chosen 10-to-one from infants who did not present with a case of pyloric stenosis and who were born in the same time frame as those in the cohort.

“More than twice as many cases as controls were bottle fed,” they wrote, at 19.5% among the cases versus 9.1% for the controls.

Maternal smoking over the 2003-to-2009 window remained relatively steady, rising to 11% from 10%.

Bottle feeding was associated with hypertrophic pyloric stenosis after adjustment for sex, maternal age, maternal race, maternal body mass index, birth order, gestational age, birth weight, and maternal smoking. Sex and maternal smoking also failed to modify the effect of bottle feeding on risk for hypertrophic pyloric stenosis.

In addition to maternal age at birth, birth order affected the association between bottle feeding and stenosis. In children of nulliparous women, there was a 60% increased risk (95% CI 1.07-2.38). In multiparous women, there was a nearly three- and-a-half-fold increased risk (OR 3.42, 95% CI 2.23-5.24) for stenosis.

“As noted by previous authors, our results may either indicate a protective effect conferred by breast milk or an increase in risk due to bottle feeding,” they concluded, adding that other studies have found potential mechanisms of action for the effect.

For example, infant formula has higher osmolarity than breast milk and decreases gastric emptying, while breast milk contains high levels of endogenous vasoactive intestinal peptide “which may help to mediate pyloric relaxation and facilitate gastric emptying.”

The study was limited by observational design, potential misclassification in the data, potential switches after birth from bottle to breastfeeding or vice versa, and patients whose mothers fed them pumped breast milk in bottles.