Snapshot A 29-year-old G2P1 female presents to labor and delivery triage with bleeding in the third trimester. Her first pregnancy was a cesarean delivery delivered at 37 weeks. She describes her bleeding as painless spotting without abdominal pain. An urgent transabdominal ultrasound is performed, showing a viable fetus and normal amniotic fluid. A transvaginal ultrasound is subsequently performed, and shows the placental edge located 1cm from the internal cervical os. Introduction Overview placenta previa is a condition characterized placental tissue extending over or < 2 cm from the internal cervical os and is associated with painless third trimester bleeding Epidemiology incidence occurs in approximately 1 per 250 births risk factors previous placenta previa previous cesarean delivery multiple gestations Associated conditions placenta previa-accreta spectrum placenta previa is present along with placenta accreta, placenta increta, or placenta percreta Presentation Most common presentation is asymptomatic finding on routine ultrasound at 16-20 weeks of gestation Symptoms painless vaginal bleeding up to 90% of cases uterine contractions, pain, and bleeding 10-20% of cases Physical exam digital vaginal examination is contraindicated until placenta previa is excluded (may result in severe hemorrhage) findings may include the following hemorrhage usually spontaneously ceases after 1-2 hours hypotension tachycardia usually no fetal distress (in contrast with vasa previa) Imaging Ultrasonography transvaginal ultrasound gold standard for diagnosis of placenta previa identification of placental tissue extending over the internal cervical os on 2nd or 3rd trimester imaging transabdominal ultrasound can be used as a screening test or in conjunction with transvaginal ultrasound if distance between edge of placenta and cervical os is ≤ 2 cm on transabdominal ultrasound, perform transvaginal ultrasound to better visualize placental position Studies Rh compatability test Complete blood cell (CBC) count Prothrombin time (PT) and activated partial thromboplastin time (aPTT) Blood type and cross Levels of fibrin split products (FSP) and fibrinogen Differential Abruptio placentae key distinguishing factors placenta prematurely separates from the uterine wall presents with painful bleeding that does not spontaneously cease Placenta accreta key distinguishing factors placenta invades the uterine wall placenta does not separate after delivery, which may lead to postpartum bleeding Vasa previa key distinguishing factors fetal vessels extend over the internal cervical os presents with fetal heart decelerations due to compression of umbilical vessels Treatment Medical monitoring in the case of asymptomatic placenta previa monitor placental position determine whether placenta accreta is also present if persistent placenta previa, plan for cesarean delivery hemostasis in the case of actively bleeding placenta previa admit for maternal and fetal monitoring achieve and maintain maternal hemodynamic stability Surgical cesarean delivery cesarean delivery should be performed in these cases active labor fetal distress (category III fetal heart rate tracing that does not respond to in utero resuscitation) inability to achieve maternal hemodynamic stability significant vaginal bleeding after 34 weeks of gestation Complications Congenital malformations associated with 2-fold increase Fetal malpresentation Vasa previa rupture of fetal vessels that cross the membranes covering the cervix cesarean delivery indicated Postpartum hemorrhage