Protective Role of Breastmilk
Breastmilk feedings are associated with a decrease in NEC in premature infants. The unique immunologic properties of breastmilk, such as secretory IgA, specific macrophages and lymphocytes, presence of nonpathogenic bacteria such as bifidobacteria, and secretory molecules with antibacterial properties, may all contribute to this protective effect.[49,50,51] Preterm infants are born before transport of most antibodies across the placenta. Because specific IgG production is delayed in newborns, and 33% of VLBW neonates have substantial hypogammaglobulinemia, the IgA content of breastmilk may be an important facet of GI mucosal protection.[3]
Breastmilk promotes the growth of bifidobacteria, which produce acetic and lactic acid that in turn inhibits the growth of many pathogenic, gram-negative organisms.[50,51] VLBW infants have a delay in the establishment of GI bifidobacteria.[50,51] This delay appears related to decreased intake of human milk.
There are a limited number of experimental studies evaluating the incidence of NEC in breastfed infants. However, they consistently report a decreased incidence of NEC. In a study of 40 neonates, 15 who were fed frozen breastmilk and then developed NEC were compared with 25 formula-fed neonates who subsequently developed NEC.[52] Those fed breastmilk were smaller, more premature, had a greater degree of perinatal stress, and required more ventilator support than their formula-fed peers. The authors concluded that frozen breastmilk did not fully protect the neonates from NEC. However, because the formula-fed neonates were at decreased risk for NEC because of their increased maturity and being less stressed, breastmilk did potentially provide some protection against NEC.
A multicenter trial provides additional evidence that breastmilk provides protection against NEC.[53] Neonates in the study were divided into groups fed only formula, those receiving formula and expressed breastmilk and those supplied with only breastmilk. The lowest incidence of NEC (1.2%) was in the group given only breastmilk, compared with 7.2% and 2.5%, respectively, in the other groups, suggesting a protective effect of breastmilk.
Various associations have been suggested between enteral feedings and the development of NEC ( Table 4 ). Consensus on a cause and effect relationship and the practical aspects of feeding preterm neonates is lacking. In a review of available information, LaGamma and Browne summarize clinical criteria for gut readiness to help answer the question of when to start and when to discontinue feedings[35] ( Table 5 ).
Adv Neonatal Care. 2003;3(3) © 2003 W.B. Saunders
Cite this: Part 1. Current Controversies in the Understanding of Necrotizing Enterocolitis - Medscape - Jun 01, 2003.
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