What type of trauma and severity causes a placental abruption?

Placental abrupt ion: Trauma to the abdomen can cause abruption, MVA, a fall, being hit, etc. In addition, hypertension; pre-eclampsia, pregnancy induced or chronic, uncontrolled hypertension can be at the root of placental abruption. Other reasons also include premature rupture of membranes, a bleed called a sub chorionic hemorrhage, placenta overlying the cervix in anyway as the cervix opens...many reasons.