PF4 and hydrops fetalis: In a multivariate Cox proportional hazard analysis including factors identified in the subanalysis of the I-PRESERVE trial (age, previous hospitalization for HF, DM, and Ln-BNP; 4 prognostic factors [PF4])[20] by forced entry methods, an sMg < 2.0 mg/dl was independently and significantly associated with HF-related events (hazard ratios [HR]: 2.365, 95% confidence intervals [CI]: 1.267–4.413, P = .007).