GDF15 and hydrops fetalis: A total of six studies evaluated the prognostic implications of serum GDF-15 in relation to all-cause mortality, adverse cardiovascular events, and HF hospitalisation with a mean follow-up duration ranging from 12 to 112 months (Tables S5–S7) (Izumiya et al., 2014; Sinning et al., 2017; Mendez Fernandez et al., 2020; Oyama et al., 2023; Yin et al., 2023; Lyu et al., 2024).