Possible origin of amniotic fluid constituents affecting thromboplastic activity.

The clotting-accelerating activity of amniotic fluid (AF) has been known for long, but a clinical importance has only recently been attributed to this phenomenon. In order to obtain some informations on the origin of AF component(s) responsible for this action, the effects on the coagulation process of extracts prepared from the placenta, fetal membranes and fetal excretes were investigated. Normal saline extracts from the placenta, the amniotic and chorionic membranes, and those from the mucus aspirated from the upper respiratory tract of the fetuses were shown to accelerate, whereas meconium extract and untreated fetal urine were found to inhibit blood coagulation. Results presented in this paper indicate that AF components affecting the thromboplastic system in one way or other may be of both fetal and extrafetal gestational tissue origin, and that the quality of the actual effect exerted on the clotting system by AF depends on the relative amount of AF constituents oppositely affecting the hemostatic system.