This study will quantify lipid peroxidation products (malondialdehyde, 4 hydroxy-2-nonenal, hexanal, and 8-iso-PGF2α), fatty acid content, and antioxidant capacity in donor human milk sampled from two neonatal units in the UK. Comparison will be made to preterm transitional/mature milk and term mature milk.

The investigators have recently identified that current human milk banking practices in the United Kingdom may have the potential to increase levels of lipid peroxidation products in donor human milk. It is therefore important to quantify the extent of this increase. This project aims to quantify for the first time the levels of lipid peroxidation products in donor human milk that is provided to infants on the neonatal unit.

Donor human milk samples will be collected from two neonatal units in the United Kingdom, served by different human milk banks. Fresh mature term breast milk, collected from healthy mothers in the community, and preterm transitional/mature breast milk, collected from healthy mothers at a neonatal unit, will be used for comparison. For each group, 10 x 5 mL samples will be analysed for the lipid peroxidation products, malondialdehyde, 4 hydroxy-2-nonenal, hexanal, and 8-iso-PGF2α. The fatty acid content and total antioxidant capacity will also be measured. All analysis will be undertaken at Bournemouth University.

Inclusion Criteria:

• Donor human milk that was intended to feed an infant at a neonatal unit in the U.K will be used for this study. Donor human milk needs to be routinely discarded 24 hours after defrosting on the unit, at that point it will be used as sample for this study.
• Preterm transitional/mature breast milk will be sampled from healthy, asymptomatic mothers of a preterm baby (born < 37 weeks gestational age) as soon as a stable milk supply is established. Samples will only be obtained if there is a surplus to the babies' need.
• Term mature breast milk will be sampled from healthy, asymptomatic mothers in the community. Samples will only be obtained if there is a surplus to the babies' need.

Exclusion Criteria:

• Donor human milk that cannot be stored on ice or in the fridge within 2 hours and cannot be frozen at -80°C within 5 hours
• For preterm and term breast milk:

Women < 18 years Women who are not able to access the study information in English Smoking women Women with mastitis Women who delivered after clinical chorioamnionitis, or other sepsis

Donor human milk is donated by mothers, having a stable milk supply, to the respective milk bank from which it is requested from the neonatal units, where it is sampled.

Preterm mothers will be selected from a neonatal unit in the U.K.

Term mothers will be selected from the community form baby cafes and similar in the Bournemouth area.