Breast-feeding success among infants with phenylketonuria

Abstract

Breast milk is the nutrition of choice for human infants (American Academy of Pediatrics, 2005; American Association of Family Physicians, 2008; Association of Women's Health Obstetric and Neonatal Nurses, 2005; Canadian Paediatric Society, 2005; U.S. Preventive Services Task Force, 2008; World Health Organization, 2009). In comparison to standard commercial formula, human breast milk has a lower concentration of protein and a lower content of the amino acid phenylalanine (Phe). For infants with phenylketonuria (PKU), these attributes of human breast milk make it ideal as a base source of nutrition. The purpose of this study was to compare the incidence and duration of breast-feeding and corresponding Phe levels of breast-fed and formula-fed infants with PKU in the caseload of a pediatric metabolic clinic at an urban tertiary-care medical center. Charts were reviewed for infants diagnosed with PKU beginning with 2005 and ending with 1980, the year no further breast-feeding cases were identified in the PKU population. During the first year of life, most of the infants, whether breast-fed or formula-fed, had similar mean Phe levels. However, the frequency distributions revealed that more breast-fed infants with PKU had Phe levels within the normal range (120-360 μmol/L) and were less likely to have low Phe levels (<120 μmol/L) than formula-fed infants with PKU. Further research is needed to understand how mothers manage breast-feeding in the context of PKU.

Figure 1. Simplified phenylalanine pathway in PKU

© Banta-Wright 2011

Figure 2. Mean Phe level for each infant by birth year

The shaded area between 120 μmol/l and 360 μmol/l represents the normative range for Phe levels for infants with PKU, and therefore, successful management of PKU.

Figure 3. Frequency Differences between Breast-fed and Bottle-fed Infants with PKU and the Probability of having a Normal (120–360 μmol/l), Low (<120 μmol/l) or High (>360μmol/l) Phe Levels

* = χ² (df = 2, N = 3,260) = 205, p < .001

Figure 4. Comparison between Breast-fed and Bottle-fed Infants with PKU living in the metropolitan area vs non-metropolitan area and the Probability of having a Normal Phe Level

Metropolitan area includes the three counties of Clackamas, Multnomah, and Washington which designates the Portland metropolitan area. The non-metropolitan area included the following regions: Willamette valley, central high mountain desert, mountainous southern, coastal, rural eastern, and adjacent southern region of the state of Washington. The shaded area between 120 μmol/l and 360 μmol/l represents the normative range for Phe levels for infants with PKU, and therefore, successful management of PKU. * = χ² (df = 1, N = 1,685) = 18.56, p < .001

Figure 5. Regional Difference in the mean Phe Levels

The shaded area between 120 μmol/l and 360 μmol/l represents the normative range for Phe levels for infants with PKU, and therefore, successful management of PKU. * = significant, F(6, 2251) = 5.2, p < .001