Etiology Uncertain(primary cause) Risk factors 1. Increased age and parity 2. Vascular diseases: preeclampsia, chronic hypertension, renal disease. 3. Mechanical factors: trauma, intercourse polyhydramnios, Supine hypotensive syndrome 5. Smoking, cocaine use, uterine myomaEtiology • Uncertain (primary cause) • Risk factors 1. Increased age and parity 2. Vascular diseases: preeclampsia, chronic hypertension, renal disease. 3. Mechanical factors: trauma, intercourse, polyhydramnios, 4. Supine hypotensive syndrome 5. Smoking, cocaine use, uterine myoma