Free Fatty Acid Concentration in Expressed Breast Milk Used in Neonatal Intensive Care Units

Preterm and sick term infants are commonly fed with expressed breast milk (EBM) that has been subjected to various storage and handling conditions before feeding that may cause lipase-mediated elevation of free fatty acids (FFA). This study was designed to describe the variation, between mothers' and within the same mother over time, in the concentration of FFA in EBM used in an Australian neonatal unit. A total of 256 EBM samples, 149 freshly expressed in the unit cot-side and 87 expressed at home and brought in to the unit, were collected from 32 mothers with an infant admitted to the neonatal intensive and/or special care units at the Women's and Children's Hospital, Adelaide. Among the fresh EBM samples collected cot-side, the average total fat content was 29.78 ± 9.28 mg/mL, and the FFA concentration was 1.70% of total fats (interquartile range [IQR]: 1.17-2.37%). Among the 10 mothers who provided fresh EBM at different stages of lactation, the concentration of FFA remained low overall, with some day-to-day variation (min 0.58% and max 5.0% of total fats within the same mother). The average total fat content of home collected EBM was similar to the cot-side collected samples, at 27.37 ± 8.23 mg/mL, and the FFA concentration was slightly higher at 2.49% of total fats (IQR: 1.74-3.29%). Overall, the FFA concentration of breast milk in the neonatal unit before and even after a short period of cold storage and handling is universally low.