Pyloric Stenosis Risk Linked to Bottle-feeding

Steven Fox

September 04, 2012

September 4, 2012 — Infants who were bottle-fed had a significantly higher incidence of pyloric stenosis (PS) compared with infants who were exclusively breast-fed, according to the results of a large, population-based Danish study of more than 70,000 infants.

The study was published online September 3 in Pediatrics.

"In this large cohort study, we found that infants who were bottle-fed had a 4.6-fold increased risk of developing PS compared with infants who were not bottle-fed, even after adjustment for other known risk factors and possible confounders," Camilla Krogh, MD, from the Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark, and colleagues write.

PS, which usually develops during the first few weeks of life, is the most common clinical condition requiring surgery among infants. Even though disease presentation, diagnosis, and treatment are well known, the causes remain unclear. Symptoms usually do not show up until the second or third week after birth, the researchers note, suggesting that early environmental factors could be a trigger.

The researchers also note that as the frequency of breast-feeding increased in Denmark during the 1990s, the incidence of PS decreased.

To investigate a possible link between bottle-feeding and development of PS, the authors examined statistics from the Danish National Birth Cohort. The cohort included data on a total of 101,042 pregnancies in 91,827 Danish women from 1996 to 2002.

In this study, researchers focused on 70,148 singleton births among women who were interviewed twice during their pregnancies (at weeks 12 and 30), and twice again after delivery (6 months and 18 months).

During the 6-month postdelivery interview, the mothers were asked whether they were presently breast-feeding. If they were, interviewers asked for how long they had exclusively been breast-feeding. If they were no longer breast-feeding, they were also asked how old their children were when they stopped breast-feeding.

For purposes of the study, the researchers assumed that any infant younger than 4 months who was not fully breast-fed was bottle-fed.

Of the 70,148 singleton infants, 65 infants required surgery for PS, 29 of whom were bottle-fed before PS diagnosis.

The overall hazard ratio (HR) for PS among infants who were bottle-fed compared with breast-fed infants was 4.62 (95% confidence interval [CI], 2.78 - 7.65).

The increased risks for PS were similar for infants who had been both breast- and bottle-fed (HR, 3.36; 95% CI, 1.60 - 7.03), formerly breast-fed (HR, 5.38; 95% CI, 2.88 - 10.06), and had never been breast-fed (HR, 6.32; 95% CI, 2.45 - 16.26; P = .76).

In addition, the researchers say, they saw a higher risk for PS among bottle-fed infants even after 30 days had elapsed since initial exposure to bottle-feeding. That elevated risk did not vary with age at initial exposure to bottle-feeding, the authors say.

"On the basis of our study, it is not possible to determine whether it is the formula or the mechanism of bottle-feeding or both that make up the high risk," the authors write. However, they note that infant formula contains higher levels of whey and casein proteins than breast milk, and therefore may be more difficult for infants to digest.

In any case, they conclude, "The result adds to the evidence supporting the advantage of exclusive breastfeeding in the first months after birth."

This study was supported by grants from the Faculty of Health Sciences at the University of Copenhagen and the Danish Agency for Science, Technology, and Innovation. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online September 3, 2012. Full text

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