Growth and pulmonary outcomes during the first 2 y of life of breastfed and formula-fed infants diagnosed with cystic fibrosis through the Wisconsin Routine Newborn Screening Program.

Background: The optimal feeding (breast milk, formula, or a combination) for infants with cystic fibrosis (CF) is unknown. Recommendations from the CF Foundation are based on limited data.

Objective: We compared growth and pulmonary outcomes between breastfed and formula-fed infants through the age of 2 y.

Design: A total of 103 CF infants born in 1994-2006 and diagnosed through newborn screening in Wisconsin were studied. Breastfed infants were classified by the duration of exclusive breastfeeding (ExBF). Exclusive formula-feeding (ExFM) was classified by the formula's caloric density (ie, standard [0.67 kcal/mL (20 kcal/oz) (ExFM20)] throughout infancy or high density [≥0.74 kcal/mL (22 kcal/oz) (ExFM22+)] for some duration of infancy).

Results: Fifty-three infants (51% of infants) were breastfed and 50 infants (49% of infants) were ExFM. In breastfed infants, the duration of ExBF was <1 mo (53% of infants), 1-1.9 mo (21% of infants), 2-3 mo (17% of infants), and 4-9 mo (9% of infants). In ExFM infants, 23 infants (46%) received a formula with a high caloric density; approximately half (n = 13) of the ExFM infants received the formula by 6 mo of age. Proportionately more infants with pancreatic sufficiency (n = 9) were ExBF ≥1 mo (44% of infants), and none of the infants were ExFM22+, compared with infants with meconium ileus (n = 24; 13% of infants were ExBF ≥1 mo, and 38% of infants were ExFM22+) or pancreatic insufficiency (n = 70; 25% of infants were ExBF ≥1 mo, and 20% of infants were ExFM22+) (P = 0.02). In infants with pancreatic insufficiency, weight z scores declined from birth to 6 mo (P < 0.0001) in infants who were ExBF ≥2 mo, and the number of Pseudomonas aeruginosa infections through the age of 2 y was fewer in breastfed than in ExFM infants (P = 0.003) but did not differ by the duration of ExBF.

Conclusion: For infants with CF, ExBF <2 mo does not compromise growth and is associated with a respiratory benefit.