中文摘要：

目的分析胎龄小于33周早产儿坏死性小肠结肠炎（NEC）发病时间及围产高危因素。方法回顾性分析2010年10月至2012年12月收治的49例胎龄小于33周早产儿NEC的发病时间，通过logistic回归分析NEC的围产高危因素。以确诊NEC的49例患儿为NEC组，121例非NEC早产儿为对照组，进行病例对照研究。结果49例NEC患儿发病日龄中位数为17．5d（范围3-106d）。性别、小于胎龄儿、出生方式、产前应用激素等对NEC发病无影响，而小胎龄、低出生体重和新生儿窒息可增加NEC发病风险，其中小胎龄是NEC发病的独立高危因素。结论胎龄小于33周早产儿NEC发病主要与胎龄小有关；发病日龄中位数为17．5d。

英文摘要：

Objective To study the timing of presentation and perinatal high-risk factors for necrotizing enterocolitis （NEC） in preterm infants with a gestational age of 〈33 weeks. Methods A case-control study was conducted in 49 preterm infants with NEC （gestational age 〈33 weeks） who were admitted to the Neonatal Intensive Care Unit of Beijing Bayi Children＇s Hospital between October l, 2010 and December 30, 2012, as well as preterm infants without NEC during the same period. The timing of presentation of NEC was retrospectively analyzed, and the perinatal high-risk factors for NEC were determined by multivariate logistic regression analysis. Results The median age of onset was 17.5 days （range： 3-106 d） in preterm infants with NEC. Sex, being small for gestationat age, delivery mode and antenatal corticosteroid therapy were not associated with the development of NEC; low gestational age, low birth weight and neonatal asphyxia increased the risk of NEC, and low gestational age was identified as an independent high-risk factor for the development of NEC. Conclusions Low gestational age is an important risk factor for the development NEC in preterm infants under 33 weeks＇ gestation, and the median age of onset is 17.5 days.