Osmolality of donor human milk rises dramatically within minutes of fortification with varied degrees depending on the fortifier used.

Background: The addition of fortifiers to human milk can enhance its energy and protein content, although it results in an increase in osmolality, which may vary depending on the composition of fortifiers. The manner in which osmolality changes over time remains uncertain. Aims: We hypothesized that the impact of different fortifiers on osmolality would vary significantly and evolve dynamically with the duration of place time. Methods: Osmolality measurements were taken from the donor human milk (DHM)at 3 and 22 h after the addition of six different human milk fortifiers (HMFs) using a freezing osmolality meter. Furthermore, the osmolality was evaluated at nine time points following the standard fortification procedure with HMF1-3. Results: (1) The mean osmolality of the unfortified donor milk was 299 mOsm/kg. The addition of three multi-component fortifiers (HMF1-3) led to a significant elevation in osmolality ( Conclusions: The addition of fortifiers significantly increased the osmolality of DHM. However, the degree of increase varied depending on the nutrient composition and content of the fortifiers used. It remains a challenge to avoid the rapid increase in osmolality of DHM within a very short time after the addition of a fortifier, even when fortifying at the bedside.