TNFRSF11B and hydrops fetalis: Among all the HF related biomarkers, there was a significant inverse correlation between log transformed serum OPG and trochanteric BMD in patients with HF (R = −0.299, P = 0.001) (Table 2), femoral neck BMD (R = −0.29, P = 0.002) and Ward triangle region of hip (R = −0.34, P<0.001) while there is no significant correlation between OPG and lumbar region BMD.