The placenta mediated pregnancy complications, including pre-eclampsia, birth of a small for gestational age child, placental abruption or late pregnancy loss, are common and often devastating pregnancy complications leading to important maternal/fetal/neonatal morbidity and mortality. In this narrative review I examine two common questions related to women with prior placenta mediated pregnancy complications. Do thrombophilias cause placenta mediated pregnancy complications? Does low molecular weight heparin prevent recurrent placenta mediated pregnancy complications?