GDF15 and abortion: By performing experiments using clinical samples from healthy pregnancies and unexplained RPL (URPL) patients, immortalized human trophoblast cells (HTR‐8/SVneo) and lipopolysaccharide (LPS)‐induced abortion mouse models, we discovered that growth differentiation factor 15 (GDF15), which is derived from human trophoblasts, was downregulated in villi and maternal sera from URPL patients.