TTR and hydrops fetalis: Serum prealbumin levels (R2 = 0.176) measured in the VLF (β = 0.003, p < 0.001), LF/HF ratio (β = 0.207, p = 0.001), LF (β = 0.003, p = 0.002), and HF (β = 0.006, p = 0.005) were significant predictors.