Maternal health, neonatology and perinatology towards a standardized outcome set for clinical trials in Hemolytic Disease of the Fetus and Newborn (HDFN): preliminary findings from two European advisory boards.

Hemolytic Disease of the Fetus and Newborn (HDFN) remains a serious perinatal condition worldwide despite major advances in antenatal and postnatal care. A key gap in HDFN research is the absence of a standardized outcome set, leading to inconsistent reporting and limited comparability across studies identified during systematic literature review (SLR). Outcomes important to families, such as long-term neurodevelopment and emotional impact, are often overlooked. 2 separate European advisory boards with 7 HDFN experts were conducted to explore expert perspectives on outcomes that may inform future core outcome set (COS) development. The findings should be interpreted as a preliminary, descriptive outcome prioritization exercise rather than a finalized COS, as no joint consensus meeting, Delphi process, pre-specified consensus threshold, or patient/parent involvement was undertaken. Establishing a formal COS through a structured multi-stakeholder process could enhance research quality, support future evidence generation, and promote more consistent care.Clinical trial number: Not applicable.