IL6 and hydrops fetalis: Through Pearson correlation analysis, it was shown that SDNN, RMSSD, HF, SD1, and SD2 had a strong negative correlation with MSS scores and the expression of Caspase3 (P < 0.01 or 0.05); SDNN, RMSSD, SD1, and SD2 were strongly negatively correlated with TNF-α, IL-1α, IL-6, IL-10, sCD14, HMGB1, and CD4+CD25+Treg and TH17, whereas they were positively correlated with the expression of CHAT and TH (P < 0.01 or P < 0.05).