High frequency of protein Z deficiency in patients with unexplained early fetal loss.

The protein Z-protein Z-dependent inhibitor complex is a factor Xa inhibitor. Protein Z deficiencies have recently been described in patients with ischemic stroke. As placenta infarction leads to poor pregnancy outcome, we studied protein Z plasma concentrations in nonthrombotic, nonthrombophilic consecutive patients with unexplained pregnancy wastage. A significant amount of protein Z deficiencies was only found in the early fetal loss group (< 1 mg/L; 44 of 200, P < 10(-4)) and mainly in the case of fetal demise between the beginning of the 10th and the end of the 15th week of gestation (odds ratio, 6.7 [3.1-14.8], P < 10(-3)). These deficiencies were not due to partial vitamin K1 deficiency, and at least some of them were constitutional ones. In women, protein Z deficiency may induce an enhanced risk of severe placental insufficiency soon after the connection of maternal and fetal circulations.