Snapshot A 33-year-old G4P3 presents to the obstetrician at 29 weeks gestation with painless vaginal bleeding. The bleeding began 2 hours ago and she has delivered a substantial amount of blood with clots. She is having no uterine contractions and the fetal pulse is 150/min. Her last pregnancy was delivered by emergency cesarean at 37 weeks due to double-footing breech presentation during labor. Findings on transvaginal ultrasound show the placenta extending over the internal cervical os. Epidemiology Incidence occurs in approximately 1 per 250 births location most common tricuspid valve Risk factors previous placenta previa previous cesarean delivery multiple gestations Etiology 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 Associated conditions placenta previa-accreta spectrum placenta previa is present along with placenta accreta, placenta increta, or placenta percreta Presentation Symptoms asymptomatic finding on routine ultrasound 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 Ultrasound 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 Serum labs 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