Feeding practices and the prevalence of cow's milk protein allergy in Irish preterm infants.

Background: The prevalence of cow's-milk protein allergy (CMPA) is between 2% and 3% and symptoms vary depending on underlying immune mechanism at play. Breast milk is the optimal nutrition for premature infants and breast milk fortifiers (BMF) are commonly used to optimise growth and nutrition. BMF are typically derived from cow's milk and, as such, preterm infants are exposed to cow's milk in the first weeks of life. Previously, preterm infants were suspected to have a higher risk of allergen development because of early antigen exposure and increased gut permeability. The primary aim of the present study was to evaluate the prevalence of CMPA among very preterm (<32 weeks) and/or very low birth weight (VLBW) infants. The secondary aim was to describe feeding practices, specifically the breastfeeding rates and specialist, non-standard formula use in this cohort over the first 6 months of life.

Methods: This was a retrospective study performed in a large tertiary maternity hospital (8500 deliveries/year and 110 very preterm infants/year) in Dublin, Ireland over a 3-year period, 2017-2020. Infants born very preterm and/or VLBW who were followed in the outpatient clinic until 6 months corrected gestational age (CGA) were included. Hospital ethical approval was obtained.

Results: One hundred and forty-four infants were included with a median birth weight of 1338 g. No infant had a diagnosis of CMPA when leaving the neonatal intensive care unit (NICU) but, by 6 months CGA, this increased to 1.4% (n = 2). Upon discharge from the NICU, 88 infants (61%) were receiving at least some breast milk, decreasing to 13 (9.1%) at 6 months CGA. Those who were receiving exclusive breast milk at discharge were significantly more likely to still be receiving any breast milk at three (p ≤ 0.001) and 6 months ( p ≤ 0.001) CGA compared to those combined feeding or exclusively formula feeding. At 6 months CGA, 18.9% (n = 27) were attending a dietician and 31.5% (n = 45) were using specialist, non-standard infant formula.

Conclusions: The prevalence of CMPA in this cohort was 1.4%, which is similar to the reported prevalence of CMPA in the general paediatric population. Infants who were discharged from NICU exclusively breastfeeding were more likely to be receiving any breast milk at outpatient follow-up. This highlights the importance of on going dietetic and lactation support in the outpatient setting for this vulnerable cohort.