Based on the OPLS-DA results, metabolites were selected based on the thresholds of VIP ≥ 1 and ABS (fold change) ≥ 2, and 264, 159, 397, and 234 DAMs were found in CF-vs.-HcF, HcF-vs-HF, CS-vs.-HcS and HcS-vs.-HS, respectively. The gene discussed is HCFC1; the disease is hydrops fetalis.