Placenta previa: Difference between revisions
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[[File:Placenta previa.png|thumb|Placenta previa subtypes.]] | [[File:Placenta previa.png|thumb|Placenta previa subtypes.]] | ||
*Placenta that implants over or near the internal cervical os | *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> | *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 | *Leading cause of [[Antepartum hemorrhage|antepartum hemorrhage]] in the third trimester | ||
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==Clinical Features== | ==Clinical Features== | ||
* | *Painless, bright red [[Vaginal bleeding in pregnancy (greater than 20wks)|vaginal bleeding]] — typically in late 2nd or 3rd trimester | ||
*Initial "sentinel bleed" often self-limited | *Initial "sentinel bleed" often self-limited | ||
*May present with profuse hemorrhage and [[Hemorrhagic shock|hemodynamic instability]] | *May present with profuse hemorrhage and [[Hemorrhagic shock|hemodynamic instability]] | ||
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==Evaluation== | ==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> | **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) | **Type and screen / crossmatch (prepare for massive transfusion) | ||
**[[Rh factor|Rh status]] — administer [[RhoGAM]] if Rh-negative | **[[Rh factor|Rh status]] — administer [[RhoGAM]] if Rh-negative | ||
**CBC, coagulation studies (PT/INR, fibrinogen) | **CBC, coagulation studies (PT/INR, fibrinogen) | ||
* | *Fetal monitoring — continuous cardiotocography | ||
*Consider [[Kleihauer-Betke test]] to quantify fetomaternal hemorrhage | *Consider [[Kleihauer-Betke test]] to quantify fetomaternal hemorrhage | ||
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==Disposition== | ==Disposition== | ||
*All patients with placenta previa and vaginal bleeding require | *All patients with placenta previa and vaginal bleeding require admission | ||
*Asymptomatic previa diagnosed on routine US — outpatient OB follow-up with pelvic rest | *Asymptomatic previa diagnosed on routine US — outpatient OB follow-up with pelvic rest | ||
Latest revision as of 09:35, 22 March 2026
Background
- 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
- Prior cesarean delivery or uterine surgery
- Prior placenta previa (recurrence 4-8%)
- Advanced maternal age (>35)
- Multiparity
- Cigarette smoking
- Cocaine use
- Assisted reproduction (IVF)
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
- Ectopic pregnancy
- First trimester abortion
- Complete abortion
- Threatened abortion
- Inevitable abortion
- Incomplete abortion
- Missed abortion
- Septic abortion
- Round ligament stretching
- Incarcerated uterus
- Malposition of the uterus
>20 Weeks
- Labor/Preterm labor
- Placental abruption
- Placenta previa
- Vasa previa
- Uterine rupture
- Vaginal trauma
- HELLP syndrome
- Cholestasis of pregnancy
- Chorioamnionitis
- Incarcerated uterus
- Acute fatty liver of pregnancy
- Malposition of the uterus
- Placenta accreta
- Placenta increta
- Placenta percreta
Any time
- Hemorrhagic ovarian cyst
- Fibroid degeneration or torsion
- Ovarian torsion
- Constipation
Evaluation
- Transabdominal ultrasound — first-line to confirm placental position
- Transvaginal US is safe and more accurate than transabdominal[2]
- Labs
- 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