There are significant challenges in providing donor human milk for all premature infants whose mothers are unable to provide an adequate supply of their own milk: nutrition, safety, supply, and immune protection. First, most donor human milk is provided by women who have delivered at term and have weaned their own infant but continue to pump and donate their milk in later lactation. As noted in Figure 1, this milk from mothers of term infants, several months after delivery is low in protein, fat, and many bioactive molecules compared to preterm milk provided in the first few weeks after delivery. A second challenge of providing donor milk is to minimize the potential to transmit infectious agents. For this reason, milk banks have rigid standards for screening and testing potential donors, for pasteurization, and for testing milk prior to distribution.