Medical Definition of Placenta previaPlacenta previa: A condition in which the placenta is implanted near the outlet of the uterus, so that at the time of delivery the placenta precedes the baby. Placenta previa can cause painless bleeding in the last trimester of pregnancy, and it may be a reason to perform a C-section. Also known as low 'placenta. Last Editorial Review: 6/9/2016 Back to MedTerms online medical dictionary A-Z List Need help identifying pills and medications? |


