The exact pathogenesis of placenta previa is not clear, and it is considered to be related to vascular lesions, trauma, and sudden decrease of intrauterine pressure. 1. Vascular lesions: if the pregnant woman herself suffers from some vascular diseases, such as hypertensive disorders in pregnancy, Raynaud’s syndrome, etc., it is easy to lead to placental abruption. 2. Trauma: When a pregnant woman suffers from abdominal trauma, it will lead to sudden stretching or contraction of the uterus, which may separate the placenta from the uterine wall and cause placental abruption. 3. Sudden decrease in intrauterine pressure: If the pressure in the uterine cavity drops very quickly, it can lead to sharp contractions of the uterus, and the placenta can become misaligned with the uterine wall and detach. Possible reasons for the sudden decrease in intrauterine pressure include premature rupture of membranes at term, excessive amniotic fluid, and rapid outflow of amniotic fluid after artificial rupture of membranes. In case of placenta previa, it is recommended to consult a doctor in time to find out the cause and carry out reasonable treatment under the doctor’s guidance to avoid delaying the condition.