Necrotizing enterocolitis during the first week of life: a multicentered case-control and cohort comparison study

Necrotizing enterocolitis (NEC) is rare during the first week of life; most cases occur after 2 to 4 weeks. We hypothesized that when NEC develops in the first week, certain predisposing factors and feeding practices are identifiable. To test this, we sought to identify every case of NEC diagnosed during the first week within the Intermountain Healthcare system during the most recent 6-year period.

Data were collected from neonates admitted to any Intermountain Healthcare neonatal intensive care unit (NICU) with a date of birth from 1 January 2001 through 31 December 2006. Electronic and paper records were obtained for all with a diagnosis of NEC (Bell stage >or=II) within the first 168 h. X-rays, physician notes, nursing records, laboratory reports and operative reports were subjected to critical review to reexamine the diagnosis of NEC. Among those with confirmed NEC, we recorded underlying conditions and every feeding given prior to the diagnosis of NEC. Comparisons were made with patients that did not develop NEC, yet were cared for in the same NICUs, during the same period of time, and of the same gestational ages.

A total of 28 neonates were identified electronically as having NEC during the first week. Critical review confirmed this in 21, but 5 were determined at laparotomy to have had spontaneous intestinal perforation, and 2 others were found on surgical reports to have had a congenital infarction of the colon. Total 20 of the 21 confirmed cases developed NEC while in a NICU being treated for another condition. The exception was a small-for-gestational-age neonate in a well baby nursery. Compared to 6100 controls, the 21 with early NEC were more likely to have had a meconium-positive test for illicit drug exposure (P<0.005), early onset sepsis (P<0.034) and respiratory distress (P<0.039). They were less likely than case-controls to have been fed human milk (P=0.003) and were more likely to have been fed formula exclusively (P=0.019). None who were fed human milk exclusively developed early NEC. Twelve of the twenty-one were fed (by gavage or bottle) amounts exceeding the upper limit of volumes taken by breastfed neonates.

We speculate that the prevalence of NEC during the first week could be reduced by identifying at-risk patients, feeding them human milk exclusively for the first week and using feeding volumes that do not exceed that taken by healthy breastfed neonates.