A step-by-step increasing tendency remains significant in all subjects (r = 0.197, P < 0.001), as well as in both males (r = 0.274, P < 0.001) and females (r = 0.241, P < 0.001), which indicated that higher levels of IL-34 revealed more severe symptoms of HF regardless of gender. Here, IL34 is linked to hydrops fetalis.