Placenta previa vs Placental abruption
How to tell Placenta previa and Placental abruption apart when a board question makes them look alike.
Step 2 CK pairs are in open beta while clinical review finishes. Spot an issue? Tell us.
Placenta over the internal cervical os on transvaginal ultrasound identifies placenta previa.
Side by side
Third-trimester painless vaginal bleeding with a soft nontender uterus and placenta over or near the cervical os on ultrasound.
Painful bleeding with uterine tenderness or hypertonus, frequent contractions, and possible fetal distress from premature placental separation.
Implantation in the lower uterine segment causes bleeding as the cervix effaces and the placental edge shears.
Decidual hemorrhage separates a normally implanted placenta, reducing maternal-fetal exchange and triggering uterine irritability.
Transvaginal ultrasound shows placental tissue covering or lying within 2 cm of the internal os, maternal coagulation studies are usually normal, and fibrinogen is typically preserved.
Abruption is often a clinical diagnosis; fibrinogen below 200 mg/dL suggests severe abruption with consumptive coagulopathy risk, and fetal monitoring may show recurrent late decelerations or bradycardia.
The trap
A common error is performing a digital cervical exam before placental location is known, which can trigger catastrophic hemorrhage in previa. The resolving move is ultrasound first, then branch management: previa is usually painless bleeding with sonographic placental overlap, while abruption is painful with a tender hypertonic uterus and can have concealed blood loss.
The repair move
Next best step: place two large-bore IV lines, type and crossmatch blood, and obtain immediate transvaginal ultrasound before any digital exam. If placenta previa is confirmed and mother and fetus are stable, give corticosteroids if preterm and plan cesarean at 36 to 37 weeks. If bleeding is heavy or instability develops, proceed to urgent cesarean delivery.
Try a free question
CoreA 29-year-old woman at 34 weeks presents with painless vaginal bleeding. BP 114/72 mm Hg, HR 102/min, temp 36.7 C. Uterus is soft and nontender, fetal tracing is category I. What is the next best step in management?
Show answer and explanation
Answer: B. Transvaginal ultrasound to locate placenta. In stable third-trimester bleeding, placental localization by transvaginal ultrasound is the critical first branching step before pelvic exam.
Why the other choices are tempting
- A. Wrong. Digital exam before excluding previa can trigger severe hemorrhage.
- C. Wrong. Induction is inappropriate before defining bleeding etiology and placental location.
- D. Wrong. Observation alone misses a potentially dangerous placental cause.
- E. Wrong. CT angiography is not first-line in this obstetric scenario.
Flashcards
Tap a card to flip it.
Which imaging finding confirms placenta previa in third-trimester bleeding?
Placental tissue covering the internal cervical os on transvaginal ultrasound confirms previa.
What exam pattern raises concern for placental abruption over previa?
Painful bleeding with uterine tenderness, hypertonus, and contractions favors abruption.
Quick answers
What is the fastest way to tell Placenta previa from Placental abruption?
Placenta over the internal cervical os on transvaginal ultrasound identifies placenta previa.
What is the key clue for Placenta previa?
Third-trimester painless vaginal bleeding with a soft nontender uterus and placenta over or near the cervical os on ultrasound.
What is the key clue for Placental abruption?
Painful bleeding with uterine tenderness or hypertonus, frequent contractions, and possible fetal distress from premature placental separation.
What is the common trap with Placenta previa vs Placental abruption?
A common error is performing a digital cervical exam before placental location is known, which can trigger catastrophic hemorrhage in previa. The resolving move is ultrasound first, then branch management: previa is usually painless bleeding with sonographic placental overlap, while abruption is painful with a tender hypertonic uterus and can have concealed blood loss.