**2. Epidemiology**

NEC constitutes about 2–5% of all NICU admissions. The incidence reported in 2012 by the Canadian Neonatal Network (CNN) in infants less than 33 weeks of gestational age (GA) was 5.1% [1]. In the United States the incidence is estimated to be 1–3 per 1000 live births [2, 6], while its prevalence is 0.3–2.4 per 1000 live births. There is considerable variability in incidence among different geographical locations and neonatal intensive care units [6–8]. Henry and Moss noted an overall incidence of 3–7% in 2005 [5]. A review by the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network data from 1998 to 2001 reported a 7% incidence of NEC among very low birth weight infants [9], while a more recent report from the network in 2010 documented an incidence of 11–15% in neonates < 1500 g or < 32 weeks at birth [10]. The incidence was found to be relatively unchanged at approximately 7% in infants weighing <1500 g in another report published in 2011 [11]. Ninety percent of the infants are preterm and the rest term or late preterm. Incidence and mortality are inversely related to GA and birth weight (BW). Mortality in preterm infants from NEC may be up to 30–50%, and 27% of infants require surgical intervention with an overall case fatality rate of 15% [5, 11, 12]. The mortality rate is higher in surgical NEC and African American males [13]. Forty-six percent of survivors suffer from abnormal neurodevelopment, and 12% of all cases of GI failure in children are due to NEC [14]. The risk and mortality associated with NEC were stratified according to BW and GA in a cohort of extremely premature infants in who the overall incidence was estimated to be 7.5% (**Tables 1** and **2**) [2].

Despite the variability in incidence among studies with rates ranging between 3 and 15% in VLBW infants, a relative stability in the incidence over time has been noted. Survival in NEC has not changed in the past five decades, the average mortality being 20–30% and up to 50% in infants requiring surgical management [10]. The proportion of neonates with NEC requiring surgical intervention has


**27**

*Necrotizing Enterocolitis*

weight infants [16].

**Table 2.**

**3. Etiology and risk factors**

*Risk of NEC based on gestational age.*

*DOI: http://dx.doi.org/10.5772/intechopen.85784*

also remained stable at approximately 30% [15]. The reasons for such observations are the decreasing gestational age limit for neonatal viability and increased survival of extremely premature infants with advances in neonatal care. Practice implementations, such as standardizing enteral feeding guidelines, exclusive feedings of own mother's milk, using donor breast milk when mother's milk is not available, minimizing duration of empiric antibiotics after birth, and avoiding packed red blood cells (PRBC) transfusions as well as antacid use in preterm infants, are associated with a decrease in incidence of NEC in very low birth

The exact etiology of NEC is undetermined and multiple risk factors have been forwarded. NEC occurs in a stereotypic relation at chronological age of onset to the gestational age at birth, the younger the gestation, the later the onset; and requires that the infant be fed [1, 11]. In one study the median age at onset in infants with a GA of less than 26 weeks was 23 days compared to a median age of 11 days for more mature infants with a GA of greater than 31 weeks [17]. Prematurity is the single greatest risk factor with almost 90% patients being premature. Enteral feeding is the second most common feature with over 98% of cases having a history of feeding. However, rate of advancement unless excessive, trophic, and early versus late and colostrum feeding are not conclusively proven to have any effect on the occurrence of NEC [18]. Other suggested risk factors are the 5 min Apgar score < 7, outborn status, body temperature 0f 36°C at 1 h of age, cesarean section, use of indomethacin with or without dexamethasone, sepsis, use of inotropes, severe metabolic acidosis, patent ductus arteriosus (PDA), gastroschisis, severe anemia, polycythemia, packed red blood cell (PRBC) transfusion, use of H2 antagonist, exposure to empirical antimicrobials, and black and Hispanic ethnicity [19]. Approximately 10% of cases occur in term and late preterm infants. Risk factors for NEC in term infants are nonhuman milk feeding; preexisting illnesses, such as congenital heart disease; primary gastrointestinal disorders; sepsis; polycythemia; respiratory disease; hypotension; neonatal

**Table 1.** *Risk and mortality associated with NEC based on birth weight.* *Necrotizing Enterocolitis DOI: http://dx.doi.org/10.5772/intechopen.85784*


#### **Table 2.**

*Pediatric Surgery, Flowcharts and Clinical Algorithms*

enterocolitis continue to be high.

to be 7.5% (**Tables 1** and **2**) [2].

*Risk and mortality associated with NEC based on birth weight.*

**2. Epidemiology**

to multisystem failure and death [2]. About one third of the cases require surgical intervention due to intestinal perforation and gangrene [5]. NEC is the commonest gastrointestinal (GI) disorder of preterm newborn infants, although term infants can be affected. NEC is associated with significant adverse outcomes, and approximately half of the survivors suffer from abnormal neurodevelopment independent of maturational status at birth. It is one of the most important causes of intestinal failure in children. Despite substantial advances in its diagnosis, prevention, and management strategies, the incidence has not changed, especially in very low birth weight neonates, and the morbidity and mortality associated with necrotizing

NEC constitutes about 2–5% of all NICU admissions. The incidence reported in 2012 by the Canadian Neonatal Network (CNN) in infants less than 33 weeks of gestational age (GA) was 5.1% [1]. In the United States the incidence is estimated to be 1–3 per 1000 live births [2, 6], while its prevalence is 0.3–2.4 per 1000 live births. There is considerable variability in incidence among different geographical locations and neonatal intensive care units [6–8]. Henry and Moss noted an overall incidence of 3–7% in 2005 [5]. A review by the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network data from 1998 to 2001 reported a 7% incidence of NEC among very low birth weight infants [9], while a more recent report from the network in 2010 documented an incidence of 11–15% in neonates < 1500 g or < 32 weeks at birth [10]. The incidence was found to be relatively unchanged at approximately 7% in infants weighing <1500 g in another report published in 2011 [11]. Ninety percent of the infants are preterm and the rest term or late preterm. Incidence and mortality are inversely related to GA and birth weight (BW). Mortality in preterm infants from NEC may be up to 30–50%, and 27% of infants require surgical intervention with an overall case fatality rate of 15% [5, 11, 12]. The mortality rate is higher in surgical NEC and African American males [13]. Forty-six percent of survivors suffer from abnormal neurodevelopment, and 12% of all cases of GI failure in children are due to NEC [14]. The risk and mortality associated with NEC were stratified according to BW and GA in a cohort of extremely premature infants in who the overall incidence was estimated

Despite the variability in incidence among studies with rates ranging between 3 and 15% in VLBW infants, a relative stability in the incidence over time has been noted. Survival in NEC has not changed in the past five decades, the average mortality being 20–30% and up to 50% in infants requiring surgical management [10]. The proportion of neonates with NEC requiring surgical intervention has

**26**

**Table 1.**

*Risk of NEC based on gestational age.*

also remained stable at approximately 30% [15]. The reasons for such observations are the decreasing gestational age limit for neonatal viability and increased survival of extremely premature infants with advances in neonatal care. Practice implementations, such as standardizing enteral feeding guidelines, exclusive feedings of own mother's milk, using donor breast milk when mother's milk is not available, minimizing duration of empiric antibiotics after birth, and avoiding packed red blood cells (PRBC) transfusions as well as antacid use in preterm infants, are associated with a decrease in incidence of NEC in very low birth weight infants [16].
