Human milk (HM) is the ideal source of nutrients for infants, but its composition is highly variable. When not enough own mother's milk (OMM) is available, the administration of pasteurized donor human milk (DHM) is considered the best alternative for feeding preterm infants (PI). The aim of this study is to evaluate the influence of diet, lifestyle habits, psychological stress, and pasteurization on the milk composition, and how it modulates infant's growth, health, and development. NUTRISHIELD is a prospective mother-infant birth cohort in the Spanish-Mediterranean area including three groups: PI <32 weeks of gestation (i) exclusively receiving OMM (i.e., >80% v/v of total intake), and (ii) exclusively receiving DHM, and (iii) term infants (TI) exclusively receiving OMM, as well as their mothers, and HM donors. Biological samples and nutritional, clinical, and anthropometric characteristics are collected at six time points covering the period from birth and until six months of infant's age (complete enteral nutrition (CEN) / recovery birth weight (RBW), and one, two, three, and six months). An additional assessment at two years (corrected age for PI) is conducted, in order to study long-term effects on neurodevelopment.

The genotype, metabolome, and microbiota as well as the HM composition (i.e., macronutrients, fatty acids, vitamins, human milk oligosaccharides, and steroids) are characterized. Portable sensor prototypes for the analysis of HM and urine are benchmarked. Additionally, maternal psychosocial status is measured at the beginning of the study and at month six, including social support, family functioning, perceived stress, anxiety, and depression symptoms, and traumatic life events. Mother-infant postpartum bonding and parental stress is also examined. At six months (corrected age for preterm groups), infant neurodevelopment scales are applied. Mother's concerns and attitudes to breastfeeding are also registered through a specific questionnaire at CEN/RBW and six months. An additional assessment at two years (corrected age for PI) is conducted, in order to study long-term effects on neurodevelopment. Current knowledge on the importance of diet and other environmental factors for infant growth, health, and development is limited and donor-matching at HM banks is frequently only based on gestational age and total protein content of HM. NUTRISHIELD provides an in-depth longitudinal study of the mother-infant-microbiota triad combining multiple biological matrices, newly developed analytical methods, and ad-hoc designed sensor prototypes with a wide range of clinical outcome measures. Data obtained from this study will be used to train a machine-learning algorithm for providing dietary advice to lactating mothers and will be implemented in a user-friendly platform based on a combination of user-provided information and biomarker analysis. A better understanding of the factors affecting the milk's composition, together with the health implications for infants plays an important role in developing improved strategies of nutraceutical management in infant care.

Inclusion Criteria:

• Acceptance of the mother to participate and sign an informed consent form
• A gestational age < 32 weeks for the group of PI and > 37 weeks for the group of TI
• Exclusive consumption (i.e., >80% v/v of total intake) of either OMM or DHM.

Exclusion Criteria:

• Non-compliance with any of the inclusion criteria
• The requirement of a special diet for the mother (e.g., celiac disease, diabetes) or maternal consumption of probiotics
• The need of intestinal surgery, severe congenital malformations, or chromosomopathies of the infant
• Mother's residence outside the Valencian Community
• Severe language barriers hampering the collection of necessary data from mothers not speaking Spanish and/or English

Three mother-infant groups were enrolled, i.e., PI-OMM, PI-DHM, and TI-OMM, and their mothers.