Placenta previa: Difference between revisions

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==Background==
==Background==
#Placenta that extends near, partially over, or beyond the internal cervical os
[[File:2910 The Placenta-02.jpg|thumb|Normal placental anatomy.]]
##Can be total, partial, or marginal
[[File:Placta prv.jpg|thumb|Schematic of placenta previa.]]
#Do NOT perform digital or speculum exam
[[File:Placenta previa.png|thumb|Placenta previa subtypes.]]
*Placenta that implants over or near the internal cervical os
**Complete — entirely covers the os
**Partial — partially covers the os
**Marginal — edge within 2 cm of the os
*Occurs in ~0.5% of pregnancies at term<ref name="cress">Cresswell JA, et al. Prevalence of placenta praevia by world region: a systematic review and meta-analysis. ''Trop Med Int Health''. 2013;18(6):712-724. PMID 23551357.</ref>
*Leading cause of [[Antepartum hemorrhage|antepartum hemorrhage]] in the third trimester
*'''Do NOT perform digital or speculum exam''' — may provoke life-threatening hemorrhage


==Risk Factors==
==Risk Factors==
#Uterine sx
*Prior [[cesarean delivery]] or uterine surgery
#Advanced maternal age
*Prior placenta previa (recurrence 4-8%)
#Cigarette smoking
*Advanced maternal age (>35)
#Cocaine abuse
*Multiparity
*[[Cigarette smoking]]
*[[Cocaine]] use
*Assisted reproduction (IVF)


==Diagnosis==
==Clinical Features==
*Painless vaginal bleeding
*Painless, bright red [[Vaginal bleeding in pregnancy (greater than 20wks)|vaginal bleeding]] — typically in late 2nd or 3rd trimester
*US
*Initial "sentinel bleed" often self-limited
**Shows position of placenta
*May present with profuse hemorrhage and [[Hemorrhagic shock|hemodynamic instability]]
*Uterus is soft and non-tender (distinguishes from [[Placental abruption|abruption]])
*Fetal heart tones usually normal unless maternal shock present
 
==Differential Diagnosis==
{{Abdominal Pain Pregnancy DDX}}
 
==Evaluation==
*[[Transabdominal ultrasound]] — first-line to confirm placental position
**Transvaginal US is safe and more accurate than transabdominal<ref name="bhide">Bhide A, et al. Placental praevia: diagnosis and management. ''Green-top Guideline No. 27a, RCOG''. 2018. PMID 35852513.</ref>
*Labs
**Type and screen / crossmatch (prepare for massive transfusion)
**[[Rh factor|Rh status]] — administer [[RhoGAM]] if Rh-negative
**CBC, coagulation studies (PT/INR, fibrinogen)
*Fetal monitoring — continuous cardiotocography
*Consider [[Kleihauer-Betke test]] to quantify fetomaternal hemorrhage


==Management==
==Management==
#Type + cross
===Hemodynamically Unstable / Active Hemorrhage===
#CBC
*Aggressive IV fluid resuscitation with crystalloid
#Coags
*Activate [[Massive transfusion protocol|massive transfusion protocol]] as needed
*'''Emergent cesarean delivery''' — consult OB/GYN immediately
*Goal: maternal stabilization takes priority
 
===Stable Patient===
*Admit to labor and delivery
*Strict bed rest, NPO
*Continuous fetal monitoring
*OB/GYN consultation for delivery planning
*If preterm (<34 weeks): [[Betamethasone|antenatal corticosteroids]] for fetal lung maturity
*If preterm with contractions: [[Tocolytics|tocolysis]] may be considered
 
==Disposition==
*All patients with placenta previa and vaginal bleeding require admission
*Asymptomatic previa diagnosed on routine US — outpatient OB follow-up with pelvic rest


==Treatment==
==See Also==
#C-section
*[[Placental abruption]]
*[[Vaginal Bleeding (Main)]]
*[[Vasa previa]]
*[[Postpartum hemorrhage]]


==Source==
==References==
Tintinalli
<references/>


[[Category:OB/GYN]]
[[Category:OBGYN]]

Latest revision as of 09:35, 22 March 2026

Background

Normal placental anatomy.
Schematic of placenta previa.
Placenta previa subtypes.
  • Placenta that implants over or near the internal cervical os
    • Complete — entirely covers the os
    • Partial — partially covers the os
    • Marginal — edge within 2 cm of the os
  • Occurs in ~0.5% of pregnancies at term[1]
  • Leading cause of antepartum hemorrhage in the third trimester
  • Do NOT perform digital or speculum exam — may provoke life-threatening hemorrhage

Risk Factors

Clinical Features

  • Painless, bright red vaginal bleeding — typically in late 2nd or 3rd trimester
  • Initial "sentinel bleed" often self-limited
  • May present with profuse hemorrhage and hemodynamic instability
  • Uterus is soft and non-tender (distinguishes from abruption)
  • Fetal heart tones usually normal unless maternal shock present

Differential Diagnosis

Abdominal Pain in Pregnancy

The same abdominal pain differential as non-pregnant patients, plus:

<20 Weeks


>20 Weeks


Any time

Evaluation

  • Transabdominal ultrasound — first-line to confirm placental position
    • Transvaginal US is safe and more accurate than transabdominal[2]
  • Labs
    • Type and screen / crossmatch (prepare for massive transfusion)
    • Rh status — administer RhoGAM if Rh-negative
    • CBC, coagulation studies (PT/INR, fibrinogen)
  • Fetal monitoring — continuous cardiotocography
  • Consider Kleihauer-Betke test to quantify fetomaternal hemorrhage

Management

Hemodynamically Unstable / Active Hemorrhage

  • Aggressive IV fluid resuscitation with crystalloid
  • Activate massive transfusion protocol as needed
  • Emergent cesarean delivery — consult OB/GYN immediately
  • Goal: maternal stabilization takes priority

Stable Patient

  • Admit to labor and delivery
  • Strict bed rest, NPO
  • Continuous fetal monitoring
  • OB/GYN consultation for delivery planning
  • If preterm (<34 weeks): antenatal corticosteroids for fetal lung maturity
  • If preterm with contractions: tocolysis may be considered

Disposition

  • All patients with placenta previa and vaginal bleeding require admission
  • Asymptomatic previa diagnosed on routine US — outpatient OB follow-up with pelvic rest

See Also

References

  1. ↑ Cresswell JA, et al. Prevalence of placenta praevia by world region: a systematic review and meta-analysis. Trop Med Int Health. 2013;18(6):712-724. PMID 23551357.
  2. ↑ Bhide A, et al. Placental praevia: diagnosis and management. Green-top Guideline No. 27a, RCOG. 2018. PMID 35852513.
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