Electrophoretic and functional characteristics of the von Willebrand factor in human fetal plasma

Although the haemostatic role of von Willebrand factor (vWF) in adults is well known, there is little information currently available about its possible contribution to in utero haemostasis. We have investigated the distribution of vWF multimers in 27 pure fetal platelet-poor plasma (FP) samples aged from 20 to greater than 36 weeks, by using electrophoresis in both low- and high-resolution agarose gels in the presence of sodium dodecyl sulphate. Our data confirm that most FP samples contain higher molecular weight (HMW) vWF multimers than those present in normal adult plasma, the proportion of these HMW forms being lower in FP samples aged greater than 36 weeks. However, we found that the multimeric unit and the protomeric form of vWF were similar in normal fetal and adult plasma. Functional assays of vWF were performed on three pooled FP samples. In all cases, fetal vWF was able to interact with factor VIII and to bind to GP Ib platelet receptor in the presence of ristocetin and to types I and III collagen. These results indicate that plasma vWF has already acquired in fetal life the functional activities required for its role in both coagulation and primary haemostasis.