What are the management and treatment options for a pregnant woman with placenta previa?

Management and Symptoms of Placenta Previa

Symptoms and Presentation

Placenta previa typically presents with painless vaginal bleeding in the second half of pregnancy, occurring in approximately 0.4% of third-trimester pregnancies. 1

• Bleeding is usually associated with uterine contractions and may be recurrent 2
• Women with one episode of bleeding are at increased risk for subsequent bleeding episodes 1
• The condition is common in early pregnancy (42.3% at 11-14 weeks) but most cases resolve by 28 weeks 1

Diagnostic Approach

Transvaginal ultrasound is the gold standard for diagnosis, with 90.7% sensitivity and 96.9% specificity. 3, 4

• Begin with transabdominal ultrasound screening, followed by transvaginal ultrasound for definitive assessment 3, 4
• Measure the distance from the leading placental margin to the internal cervical os; overlap of ≥15 mm at mid-trimester predicts persistence at delivery 3, 4
• Digital pelvic examination must be avoided until placenta previa has been excluded, as it can trigger life-threatening hemorrhage 1, 3, 4
• Use Doppler ultrasound to identify vasa previa and assess placental blood flow patterns 4

Critical Risk Assessment for Placenta Accreta Spectrum

All women with placenta previa and prior cesarean deliveries must be evaluated for placenta accreta spectrum disorder, which dramatically increases morbidity. 1, 3

• Risk increases exponentially: 7-fold after one prior cesarean to 56-fold after three cesarean deliveries 1, 3, 4
• Additional risk factors include advanced maternal age, high parity, prior uterine surgery, prior postpartum hemorrhage, Asherman syndrome, uterine anomalies, smoking, hypertension, and in vitro fertilization 1, 3, 4
• MRI may be helpful for posterior placenta previa or suspected placenta percreta 1, 4

Antepartum Management

Activity Restrictions

• Women with asymptomatic placenta previa can continue moderate-to-vigorous physical activity before 28 weeks 1, 3
• After 28 weeks, avoid moderate-to-vigorous physical activity but maintain activities of daily living and low-intensity activity such as walking 1, 3, 4
• Hospitalization is required for active bleeding 1, 3, 4

Follow-Up Protocol

• Schedule ultrasound examinations at approximately 18-20 weeks, 28-30 weeks, and 32-34 weeks to assess for previa resolution, placental location, and possible bladder invasion 4
• Early referral to a level III or IV maternal care facility is advised if placenta previa persists at the 28-30 week ultrasound 4

Anemia Optimization

• Maximize hemoglobin values during pregnancy by treating anemia with oral or intravenous iron as needed 1, 4

Delivery Planning and Timing

Planned cesarean delivery at 34 0/7 to 35 6/7 weeks of gestation is recommended for uncomplicated placenta previa. 1, 3, 4

• This timing balances neonatal complications against increased maternal bleeding risk after 36 weeks 1, 4
• Delivery should not be delayed beyond 36 0/7 weeks, as approximately 50% of women with placenta accreta spectrum beyond 36 weeks require emergent delivery for hemorrhage 1, 4
• Earlier delivery is required for persistent bleeding, preeclampsia, labor, rupture of membranes, or fetal compromise 1, 3
• Administer antenatal corticosteroids when delivery is anticipated before 37 0/7 weeks 1, 4

Delivery Location and Team Assembly

Delivery must occur at a level III or IV maternal care facility with adequate blood banking facilities and multidisciplinary expertise. 1, 4

• Essential team members include maternal-fetal medicine subspecialists, pelvic surgeons, urologists, interventional radiologists, obstetric anesthesiologists, and neonatologists 1, 4
• Notify the blood bank in advance due to frequent need for large-volume blood transfusion 1, 4
• Ensure blood bank capabilities for massive transfusion protocols 1, 4

Intraoperative Management

Surgical Approach

• Preoperative coordination with anesthesiology, maternal-fetal medicine, neonatology, and expert pelvic surgeons is essential 1, 4
• Consider dorsal lithotomy positioning to allow vaginal access and optimal surgical visualization 1
• Inspect the uterus after peritoneal entry to determine placental location and optimize uterine incision approach 1
• Make the uterine incision away from the placenta when possible 1, 3
• For suspected bladder involvement, consider ureteric stent placement and collaboration with urologic surgeons 1, 4

Management of Placenta Accreta Spectrum

• After delivery of the fetus, leave the placenta in situ if there is evidence of abnormal placental attachment 1
• Forced placental removal should never be attempted, as this causes profuse hemorrhage 1, 3, 5
• Cesarean hysterectomy may be necessary for placenta accreta spectrum 1, 3, 4

Hemorrhage Management

Activate massive transfusion protocol early rather than late. 3

• Transfuse packed red blood cells, fresh frozen plasma, and platelets in a 1:1:1 to 1:2:4 ratio for acute hemorrhage 1, 4
• Keep patients warm (>36°C) during surgery, as many clotting factors function poorly at lower temperatures 1
• Re-dose prophylactic antibiotics if blood loss ≥1,500 ml 1, 4
• Baseline laboratory assessment at bleeding initiation should include platelet count, prothrombin time, partial thromboplastin time, and fibrinogen levels 1, 4
• Consider tranexamic acid to reduce blood loss 3, 4

Postoperative Care

• Intensive hemodynamic monitoring in the early postoperative period is recommended, often best provided in an intensive care unit setting 1, 3, 4
• Close monitoring of volume status, urine output, blood loss, and hemodynamics is critical 1, 4
• Maintain a low threshold for reoperation if ongoing bleeding is suspected 1, 3, 4
• Ensure adequate iron supplementation and follow-up of hemoglobin levels if significant blood loss occurred 1, 4

Critical Pitfalls to Avoid

• Failure to diagnose placenta accreta spectrum in women with placenta previa and prior cesarean deliveries can lead to catastrophic hemorrhage 1, 3
• Digital examination without excluding placenta previa can trigger life-threatening bleeding 3, 4
• Delayed activation of massive transfusion protocol worsens outcomes 3
• Attempting manual placental removal in placenta accreta causes profuse hemorrhage 1, 5