Why does placental abruption occur?

Placental abruption may be caused by a history of trauma or gestational hypertension, but it more commonly occurs in twin pregnancies or cases of premature rupture of membranes, where abnormal intrauterine pressure often leads to placental abruption. Premature rupture of the fetal membranes can result in a sudden outflow of large amounts of amniotic fluid, reducing the size of the uterine cavity and potentially causing early placental separation. Advanced maternal age, multiparity, and maternal habits such as smoking or abnormal drug metabolism also increase the risk of placental abruption.