Two major signs of placental disease are chronic hypoxia and trophoblast invasions. SARS-CoV-2 interacts with trophoblasts. Fusion, proliferation, angiogenesis, immune tolerance, and tissue survival are some of the critical functions involved in the physiological and pathological processes of placenta development. Strikingly, some of these properties are  shared by envelope glycoproteins of retroviruses. 

Syncytin-1 (the ERV protein) is involved in physiological processes not only in placenta but also in other organs, based on evidence of fusion/differentiation, immunomodulation, apoptosis, and proliferation properties. Altered states of this protein may contribute to human placenta pathologies, including Down syndrome, preeclampsia/hemolysis, elevated liver enzymes, and low platelets syndrome/intrauterine growth restriction, and gestational trophoblastic diseases including mole and choriocarcinoma. 

This can all lead to pro-coagulator molecules being released into the blood stream causing action of the coagulator cascade, resulting in a "fetus attack." In addition to the heart (heart attack) or brain (stroke) being infarcted, the fetus may be as well. 

Diabetes Mellitus is a risk factor for this condition as is chronic high blood pressure. What is most remarkable is that, like COVID, being UNDERWEIGHT or OVERWEIGHT is a risk.

Another fascinating aspect of this protein is that it is involved with disease at the end of life. Neurodegeneration. The same ERV is implicated in MS, ALS and Alzheimer's.