CD19 and hydrops fetalis: No significant difference was observed in the percentage of CD19+ B cells (4.65 ± 4.00% for the DCM group vs. 6.04 ± 3.97% for the HF group vs. 5.67 ± 3.78% for the HC group, respectively, P = 0.46) (Additional file 1: Fig. S1 A, B) and CD20+ B cells (4.72 ± 3.42% vs. 6.61 ± 4.72% vs. 5.50 ± 2.76%, P = 0.24) among the three groups (Additional file 1: Fig. S1 C, D).