Updated: 9/27/2022

Placenta Previa

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  • 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

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(M2.OB.17.4867) A 39-year-old G4P3 woman 38 weeks pregnant presents to the emergency department with bright red vaginal bleeding that started one hour ago following sexual intercourse with her partner. She denies any abdominal pain. Her medical history is notable for three prior cesarean sections. She has not seen an obstetrician because she felt similar to her previous pregnancies. Her temperature is 98.6°F (37°C), blood pressure is 100/70 mmHg, pulse is 95/min, and respirations are 20/min. The fetal pulse is 130/min; its tracing is shown in Figure A. The patient's physical exam is unremarkable. Inspection of the vagina reveals no active bleeding. The transvaginal ultrasound machine is being prepared. What is the most likely diagnosis?

QID: 109556
FIGURES:

Vasa previa

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(0/9)

Uterine rupture

0%

(0/9)

Placenta previa

100%

(9/9)

Placental abruption

0%

(0/9)

Cord prolapse

0%

(0/9)

M 6 C

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(M2.OB.14.16) A 28-year-old G2P1 woman at 29 weeks gestation presents to the obstetrician after noticing red spots on her undergarments over the past week. Her vaginal bleeding has not been painful; however, she is concerned that it has persisted. Her previous child was born by cesarean section and she is currently taking folate and a multivitamin. She endorses feeling fetal movements. Her temperature is 98.9°F (37.2°C), blood pressure is 120/84 mmHg, pulse is 88/min, respirations are 17/min, and oxygen saturation is 99% on room air. Physical exam is notable for a gravid uterus and non-tender abdomen. Speculum exam reveals a closed cervical os and a small amount of blood. Which of the following is the most likely diagnosis?

QID: 105186

Placenta percreta

0%

(0/13)

Placenta previa

62%

(8/13)

Placental abruption

23%

(3/13)

Uterine rupture

0%

(0/13)

Vasa previa

8%

(1/13)

M 6 E

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