**Background:** Mother's own milk (MOM) is the optimal nutrition for all newborns, particularly for very low birth weight (VLBW) preterm infants (<1,500 g). VLBW infants fed exclusively with MOM have lower risks of necrotising enterocolitis (NEC), late onset sepsis (LOS), retinopathy of prematurity (ROP), and bronchopulmonary dysplasia (BPD), as well as improved neurologic outcomes. When MOM is unavailable, human donor milk (HDM) is the recommended alternative over formula. However, mothers of preterm infants face physiological and psychological barriers to lactation, including mother-infant separation, stress, and the need for mechanical pumping. In Germany, there is currently no structured lactation support for mothers of preterm infants, and human donor milk banks (HDMBs) are implemented in only a few NICUs. The legal status of donor milk in Germany remains unclear, and guidelines for HDMB operation are outdated.
**Methods:** The Neo-MILK study employs a multidisciplinary, mixed-methods approach across multiple work packages (WP) to develop an intervention for structured breastfeeding and lactation support, adapted to German NICUs and VLBW infants. WP A1 involves a sequential exploratory mixed-methods survey of mothers of VLBW infants. At least 12 semi-structured qualitative interviews will be conducted with mothers 3–12 months after hospital discharge, covering breastfeeding intention, pumping behavior, NICU stay experiences, lactation support, psychological stress, and app preferences. Interviews will be conducted remotely by a psychologist, transcribed, anonymized, and coded by two trained research assistants. Based on these interviews and literature, a paper-pencil questionnaire will be developed for an anonymous cross-sectional survey of approximately 2,000 mothers (expected 30% response rate) whose infants are 6–18 months old, identified via ICD-10 codes (P07.01, P07.02, P07.10, P07.11) from four statutory health insurers covering 28% of the German market. WP A2 is a Germany-wide postal survey of all Level I and Level II NICU leaders (n=211 physicians and n=211 nurses) assessing perceived value of MOM/HDM, current lactation support practices, HDMB implementation status, and barriers/facilitators. A response rate of at least 65% is expected. WP A3 uses a sequential explanatory design to survey all 34 known HDMBs in Germany via an anonymous online survey, followed by at least six qualitative interviews with purposefully selected respondents. WP B involves developing a comprehensive manual on human milk, breastfeeding, and lactation for staff training, along with a seven-module video-based training program and a condensed crash course, with a certificate and public recognition poster as incentives. WP C develops a multi-tool intervention package including checklists for prepartal consultation (based on the WHO Surgery Checklist), a question prompt sheet for parents, and 'mom bags' containing equipment and informational flyers. WP D involves developing a progressive web application with a media agency to help mothers document milk volume, receive pumping reminders, and access evidence-based information, developed through user experience design including personas, wireframes, and an interactive prototype pretested with the target group. WP E addresses the unclear legal classification of human donor milk in Germany, examining regulatory obligations and EU-level developments (European Commission draft regulation COM/2022/338 final on substances of human origin, July 2022). WP F develops a manual for HDMBs with practice-oriented hygienic and infection guidelines based on international guidelines, national recommendations, and scientific literature, evaluated via a Delphi technique, plus a Hazard Analysis and Critical Control Point (HACCP) concept.
**Key Results:** This is a protocol paper describing the study design and methods; no results are presented. The intervention development is ongoing and participatory, involving physicians, nurses, psychologists, sociologists, and behavioral economists, with input from parent representatives and a scientific advisory board. The preliminary intervention elements include: a written standard operating procedure for breastfeeding promotion; interdisciplinary training for midwives, nurses, and physicians; prenatal education of mothers and family members (possible in approximately 50% of cases with sufficient lead time); support for early and continuous skin-to-skin contact; early initiation of first milk expression; exclusive administration of MOM/HDM unless medically contra-indicated; and a supportive app. The intervention will be implemented and evaluated in 15 NICUs.
**Clinical Implications:** If successful, the Neo-MILK intervention will provide the first structured, evidence-based lactation and breastfeeding support program specifically adapted for mothers of VLBW preterm infants in German NICUs, combined with standardized guidelines for HDMB implementation. This has the potential to increase the proportion of VLBW infants receiving MOM, thereby reducing the incidence of NEC, LOS, ROP, and BPD, and improving long-term neurodevelopmental outcomes. The legal and hygienic guidelines developed may also clarify the regulatory framework for donor milk banking in Germany, facilitating wider HDMB implementation. The participatory, multi-stakeholder approach enhances the likelihood of real-world adoption and sustainability.