PER3 and hydrops fetalis: The variation of mRNA level in hub genes ARNTL, PER3, CRY2, BHLHE41 and NPAS2 was detected using the peripheral blood of the participants by quantitative RT-PCR, which for CRY2 and BHLHE41 showed significant increase, whereas decrease for ARNTL and NPAS2 in the HF group in comparison to the control (P < 0.001); PER3 mRNA showed a slight higher expression in the HF group (n = 21) in comparison to the control group (n = 10), while no significant difference was found (P = 0.118) (Fig. 7), which is similar to the outcomes from our bioinformatics analysis.