Epidemiology of necrotizing enterocolitis - Part II: Risks and susceptibility of premature infants during the surfactant era: A regional study

Objectives: We observed a reduced incidence of necrotizing enterocolitis (NEC) despite increased survival of extremely premature infants over the last two decades. A different susceptibility pattern to NEC according to gestation has been proposed. We aim to examine the influence of perinatal risk factors for NEC in infants less than 32 weeks gestation, in our region, in the post-surfactant era. Methods: NEC incidence, perinatal risk factors and neonatal outcomes were examined in a cohort of 4649 infants of 24-31 weeks gestation from the Neonatal Intensive Care Unit Study (NICUS) database, admitted during 1994-99. Results: A total of 178 (3.8%) infants developed NEC. More 24-27 weeks infants than 28-31 weeks infants had NEC (6.6% vs 2.6%, P < 0.001). Although low gestation infants had higher mortality and surgery need, post-operative survival (60%) was comparable to the higher gestation infants. NEC in the higher gestation group tended to be associated with perinatal risk factors, while risk factors were equally common in low gestation infants who developed NEC or not. Overall, gestation (P < 0.001), small for gestational age (P= 0.008), hyaline membrane disease (P < 0.001), placental abruption (P= 0.002) and earlier year of birth (P= 0.03) were independently associated with increased odds of NEC. Maternal hypertensive disease of pregnancy was associated with reduced NEC risk (P= 0.02). Conclusions: The incidence of NEC continues to decrease in the surfactant era and the pattern of susceptibility to NEC is based on gestational age grouping and risk factors. The reduced risk associated with hypertensive disease of pregnancy is unexplained.