Fortification of human milk can result in increased osmolality, which may have negative consequences on premature babies. The purpose of this study was to see how to target fortification affected the osmolality and microbiological safety of donor human milk and raw mature milk over the first 72 hours of storage. In a laminar flow hood, we performed target fortification on 63 pasteurized donor human milk (PDHM) and 54 raw mature milk (RMM) samples. Osmolality (mOsm/kg) was measured before fortification (T0), immediately after fortification (T1), six hours (T2), twenty-four hours (T3), forty-eight hours (T4), and seventy-two hours (T5) following fortification. T0, T4, and T5 microbiological analyses were carried out. Mean osmolality for PDHM and RMM at each study point was: T0: 291.4 11.0 vs 288.4 5.6; T1: 384.8 16.7 versus 398.3 23.7; T2: 393.9 17.7 versus 410.1 27.0; T3: 397.8 17.6 versus 417.9 26.1; T4: 400.0 16.5 versus 420.2 24.9; T5: 399.6 16.5 versus 425.2 25.8 Microbiological tests for PDHM were negative at all study sites. At T0, 16.1% of RMM samples showed positive cultures, and the bacterial count remained constant throughout the trial.

The osmolality of PDHM rises during the first 6 hours after fortification and then stabilizes and stays safe for the next 72 hours. The osmolality of RMM rises over the first 24 hours and then stabilizes and stays safe for the next 72 hours. Storage at 4°C and handling of PDHM and RMM samples in a laminar flow hood appears to be safe, preserving the microbiological safety of enriched pasteurized human milk for 72 hours.