Newborns with serious Congenital Heart Disease are at risk of intestinal injury which may present in a similar fashion to Necrotising Enterocolitis (NEC). Our local guidelines for eligibility for donor milk from our provincial milk bank include infants with significant CHD, based on the fairly robust data about NEC prevention by donor human milk, compared to formula, as a supplement to maternal milk among very preterm infants.
But is “NEC” in infants with CHD the same disease? Should we expect donor human milk to be protective for these infants?
The neonatal gut has a limited number of responses to injury, I have seen, for example, in the fairly recent past, 2 preterm babies who had a typical NEC clinical presentation, with clear pneumatosis on abdominal x-ray, who both turned out to have strangulated small intestine, one from a malrotation and the other from an internal hernia, when operated (both did well).
Diagnostic criteria for NEC in the term infant are not clear, but most studies have used the Bell criteria developed for preterm infants, and, as I am suggesting, the pathophysiology is probably different. In the preterm there is evidence that immaturity of Paneth cell development (as one example) is important, but there is no reason to believe that they are immature in babies born at term with CHD.
One of the best studies of incidence is a very recently published multicenter cohort study with over 38,000 newborns with CHD, 1,448 of them developed NEC (Spinner JA, et al. Necrotizing Enterocolitis and Associated Mortality in Neonates With Congenital Heart Disease: A Multi-Institutional Study. Pediatr Crit Care Med. 2019). The lowest frequency among infants included was for transposition of the great vessels (TGV) at 2.1%, the most frequent was among infants with hypoplastic left heart syndrome (HLHS), 5.5% :
That study noted that infants who were preterm, in addition to their CHD, had a substantially increased risk, being born before 37 weeks gestation increased the Odds of developing NEC by 1.6 among HLHS, 3.5 for TOF, and 6.5 for TGA.
A new observational study suggests that donor human milk may be useful for prevention of NEC among these infants. Cognata A, et al. Human Milk Use in the Preoperative Period Is Associated with a Lower Risk for Necrotizing Enterocolitis in Neonates with Complex Congenital Heart Disease. J Pediatr. 2019. Among 548 infants at the Texas children’s hospital in Houston, there were 1/3 who did not get fed pre-operatively. That is a frequent practice elsewhere also, for which there is really no good evidence, but concerns about gut perfusion in HLHS or severe co-arctation are reasonable, even if the ductus is wide-open on echo. They had 18 total cases of pre-operative NEC, so a limited power to say very much. Among the remaining infants, who did get fed, if they received only unfortified human milk (maternal or donor) which was about 200 babies, they had a lower incidence of NEC, only 2 cases. On multivariate analysis, human milk feeding was protective (OR 0.17, 95% CI 0.04-0.84).
This is certainly suggestive data; is there any reason to not just give donor milk, whenever supplements are required, for an infant hospitalised with CHD? The big “problem” as I see it is the large amount of milk such infants require compared to a small preterm infant. Depending on how your milk banks are organised, and how much milk they have available, three 4 kg babies with CHD could quickly drain the stocks, leaving nothing for the next thirty 400g babies!
I think the best solution is probably to ensure that preterm infants with CHD get human milk, whenever possible. If you have plenty of donor milk available, at a reasonable cost (it certainly isn’t cheap to screen and process) then giving full-term babies pasteurized donor milk is almost certainly harmless, and might reduce cases of NEC. However, a large enough RCT of donor human milk supplementation among full term babies with CHD could settle the question permanently.