The Apparent Breastfeeding Paradox: What is optimal nutrition for a premature baby?
Last week, I wrote about some of the unique challenges (and one potential solution) to breastfeeding a baby born prematurely. Another study recently published in BMJ Open provides more food for thought on breastfeeding preemies (1; full text available here).
A team of French researchers examined the relationship between breastfeeding, growth, and neurodevelopment in two observational cohorts of babies born very prematurely, at less than 32 or 33 weeks of gestation.
Between the two cohorts, a total of 2925 very preterm infants were included in the study. These babies were in the hospital for 50-60 days before they were allowed to go home. In the two cohorts, 19% and 16% of babies were breastfeeding at the time of discharge from the hospital. The study looked at associations between type of feeding at discharge (breast milk or formula), growth during hospitalization, and growth and neurodevelopment at 2 and 5 years of age.
What were the findings? In these cohorts, formula-fed babies had gained more weight by the time they were discharged from the hospital. However, at 2 and 5 years of age, the formula-fed babies scored lower on neurodevelopment assessments compared to the breastfed babies. Breastfed babies also had greater head circumferences by 2 and 5 years of age, suggesting improved brain development, and they appeared to catch up to formula-fed babies in height and weight.
The study authors call this an “apparent breastfeeding paradox.” Preemies that are breastfed early in life may be slower to gain weight, but they have better neurodevelopment in the long-term.
Feeding babies born so prematurely is tricky. Human milk evolved to meet the nutritional needs of full-term infants. Until very recently in human history, a baby born at less than 32 weeks gestation wouldn’t have survived at all. Because they need to catch up in growth and development, premature babies need more protein and minerals than human milk can provide. Previous studies not accounting for effects of breastfeeding have found that preemies with inadequate growth during hospitalization are at risk for later cognitive dysfunction. In the NICU, these preemies are fed either a special enriched formula or human milk fortified with additional nutrients. They are initially fed through a gastric tube, so it is easy to add fortifier to human milk.
The tricky part comes when premature babies start to suckle and breastfeed. This is the ultimate goal, of course, but once a baby starts to suckle on her own, supplementing with formula is a disruption to the routine of breastfeeding. It can derail the process of building milk supply and a healthy, on-demand breastfeeding relationship between mom and baby. However, there is a fear that feeding breast milk only – without the additional nutrients – may compromise baby’s growth.
As a consequence, even when a mom has established adequate milk supply and her baby is breastfeeding well, it is controversial whether she should be encouraged to supplement with enriched formula. A 2007 Cochrane review (2) attempted to address the question of whether enriched formula or human breast milk is better for preemie babies. However, the authors found NO studies of high enough quality to answer this question. This is the shortest Cochrane review I’ve ever seen – the results section is just 4 sentences! Without any convincing evidence that feeding enriched formula provides advantages to preemies, the authors conclude that moms who wish to exclusively breastfeed should be encouraged to do so.
This most recent study should give some reassurance to parents and pediatricians about the value of breastfeeding premature babies. Most importantly, it tells us that weight gain in preemies isn’t everything. Sure, it is our easiest measure of a baby’s growth and development, but feeding a preemie with breast milk may provide benefits to brain development that are not immediately apparent. At the same time, we need to be careful about over interpreting this study, because growth is clearly important as well. We need more research on what constitutes inadequate vs. adequate growth in preemies fed breast milk vs. formula.
There were some limitations to this study. Like most studies of breastfeeding, it was observational in design. That is, the babies were not randomly assigned to breastfed and formula-fed groups – that would be unethical. Many of the factors that might influence the likelihood of a mother breastfeeding might also be related to the child’s neurodevelopment. The authors attempted to statistically account for several of these confounding factors, including mothers’ age, marital status, education, profession, and income. However, we can never “fix” all of the limitations of an observational study with statistics. For example, as the authors state, “the very ability of an infant to suckle may be associated with a less sick infant.” A further limitation was that breastfeeding was only recorded at the time of discharge. For one of the cohorts, breastfeeding status was known at 2 months, but beyond that, we don’t know how long these infants were breastfed. On the other hand, a significant strength of this study was that it found the same “breastfeeding paradox” in two independent cohorts of premature babies.
The authors of the study have the following recommendation:
“In conclusion, the neurodevelopment of premature infants is likely to benefit from feeding supplemented mother’s milk during hospital stay and unsupplemented mother’s milk after discharge…”
Despite the limitations and need for further research, these findings should reassure pediatricians and encourage mothers of preemies to breastfeed when possible, while keeping a close eye on baby’s growth and development.
1. Roze, J. C., D. Darmaun, C. Y. Boquien, C. Flamant, J. C. Picaud, C. Savagner, O. Claris, A. Lapillonne, D. Mitanchez, B. Branger, U. Simeoni, M. Kaminski and P. Y. Ancel (2012). “The apparent breastfeeding paradox in very preterm infants: relationship between breast feeding, early weight gain and neurodevelopment based on results from two cohorts, EPIPAGE and LIFT.” BMJ Open 2(2): e000834.
2. Henderson, G., T. Fahey and W. McGuire (2007). “Nutrient-enriched formula milk versus human breast milk for preterm infants following hospital discharge.” Cochrane Database Syst Rev(4): CD004862.