Membranes in retroplacental hemorrhage/abruption

I have been reviewing cases of retroplacental hemorrhage/ abruption. As a result, I have become more conscious of the spiral arteries in the membranes away from the basal site of hemorrhage. I recently came across the above photographed case from a 20 week gestation stillborn with a 20% older retroplacental hemorrhage with adherent hematoma that had marked congestion and intravillous hemorrhage, and a basally directed neutrophil response. This size separation alone would not be lethal. The vessels in the membranes showed multiple laminated non-occlusive thrombi. The vessels are dilated and I can not be certain whether they are arteries or veins. There is a small amount of decidual hemorrhage. Could this be a case of maternal thrombophilia and abruption? Does thrombotic disease cause abruption by venous thrombosis and backpressure, or by arterial thrombus and subsequent hemorrhage into a basal infarction? Are these thrombi simply epiphenomenon of the abortion/ very preterm labor process?