What are the management measures for placenta previa?

Management Measures for Placenta Previa

For placenta previa, perform transvaginal ultrasound for diagnosis, avoid digital pelvic examination, hospitalize for active bleeding, restrict moderate-to-vigorous activity after 28 weeks, and plan cesarean delivery at 34-36 weeks at a tertiary center with multidisciplinary team and blood bank capabilities. 1, 2

Diagnostic Approach

Transvaginal ultrasound is the gold standard for diagnosing placenta previa with 90.7% sensitivity and 96.9% specificity. 2 Begin with transabdominal ultrasound as initial screening, then proceed to transvaginal ultrasound for definitive assessment. 3, 2

Key imaging components include:

• Measure the distance from the leading placental margin to the internal cervical os—overlap of ≥15 mm at mid-trimester predicts persistence at delivery. 2
• Evaluate the inferior placental margin, placental umbilical cord insertion, and cervix from external to internal os. 3
• Add Doppler ultrasound to identify vasa previa and assess placental blood flow patterns, as vessels overlying the internal cervical os can be subtle and require color/spectral Doppler for accurate diagnosis. 3

Critical pitfall: Digital pelvic examination must be avoided until placenta previa has been excluded, as this can trigger life-threatening hemorrhage. 1, 2

Risk Stratification 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, 2 The risk increases exponentially: 7-fold after one prior cesarean to 56-fold after three cesarean deliveries. 1, 2

Additional risk factors include:

• Advanced maternal age, high parity, prior uterine surgery, prior postpartum hemorrhage. 1, 2
• Asherman syndrome, uterine anomalies, smoking, hypertension, in vitro fertilization. 1, 2

For suspected accreta, obtain MRI after 24 weeks (optimal timing 30-35 weeks) when ultrasound findings are concerning, particularly for posterior placenta previa or suspected placenta percreta. 3, 1

Antepartum Activity Restrictions

Before 28 weeks: Women with asymptomatic placenta previa can continue moderate-to-vigorous physical activity. 1, 2

After 28 weeks: Avoid moderate-to-vigorous physical activity but maintain activities of daily living and low-intensity activity such as walking. 1, 2

Hospitalize immediately for active bleeding. 1, 2 For selected stable patients after initial bleeding episode, outpatient management may be considered with close follow-up, though this requires careful patient selection and reliable access to emergency care. 4

Anemia Optimization

Maximize hemoglobin values during pregnancy—treat anemia with oral or intravenous iron as needed to prepare for potential hemorrhage at delivery. 1, 2

Delivery Planning and Timing

Plan cesarean delivery at 34 0/7 to 35 6/7 weeks of gestation for uncomplicated placenta previa. 1, 2 This timing balances neonatal complications against increased maternal bleeding risk after 36 weeks. 1

Do not delay delivery beyond 36 0/7 weeks, as approximately 50% of women with placenta accreta spectrum beyond 36 weeks require emergent delivery for hemorrhage. 1, 2

Deliver earlier for:

• Persistent bleeding
• Preeclampsia
• Labor
• Rupture of membranes
• Fetal compromise 1

Administer antenatal corticosteroids when delivery is anticipated before 37 0/7 weeks. 1

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, 2

Essential team members include:

• Maternal-fetal medicine subspecialists
• Pelvic surgeons (gynecologic oncology or urogynecology)
• Urologists (for suspected bladder involvement)
• Interventional radiologists
• Obstetric anesthesiologists
• Neonatologists
• Blood bank capable of massive transfusion protocols
• Nursing leadership experienced in high-level postpartum hemorrhage 1

Notify the blood bank in advance due to frequent need for large-volume blood transfusion. 1, 2

Intraoperative Management

Preoperative coordination with anesthesiology, maternal-fetal medicine, neonatology, and expert pelvic surgeons is essential. 1, 2

Surgical approach:

• 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, 2
• For suspected bladder involvement, consider ureteric stent placement and collaboration with urologic surgeons. 1

Critical management for placenta accreta spectrum:

• After delivery of the fetus, leave the placenta in situ if there is evidence of abnormal placental attachment. 1
• Never attempt forced placental removal—this causes profuse hemorrhage and is associated with significant hemorrhagic morbidity. 1, 2, 5
• Cesarean hysterectomy is the most accepted approach for significant placenta accreta spectrum. 1, 5

Hemorrhage Management

Activate massive transfusion protocol early rather than late—delayed activation worsens outcomes. 2

Transfusion strategy:

• Transfuse packed red blood cells, fresh frozen plasma, and platelets in a 1:1:1 to 1:2:4 ratio when transfusing for acute hemorrhage. 1
• Re-dose prophylactic antibiotics if blood loss ≥1,500 ml. 1
• Keep patients warm (>36°C) during surgery, as many clotting factors function poorly at lower temperatures. 1

Baseline laboratory assessment at bleeding initiation should include:

• Platelet count
• Prothrombin time
• Partial thromboplastin time
• Fibrinogen levels 1

Consider tranexamic acid to reduce blood loss. 2

Postoperative Care

Intensive hemodynamic monitoring in the early postoperative period is recommended, often best provided in an intensive care unit setting. 1, 2

Monitor closely:

• Volume status
• Urine output
• Blood loss
• Hemodynamics 1, 2

Maintain a low threshold for reoperation if ongoing bleeding is suspected. 1, 2

Ensure adequate iron supplementation and follow-up of hemoglobin levels if significant blood loss occurred. 1

Follow-up Imaging

For women with placenta previa overlying a uterine scar, perform early third trimester follow-up ultrasound at 28-32 weeks. 3 Asymptomatic patients may undergo weekly or biweekly ultrasound cervical length and placental edge thickness measurements to predict antepartum bleeding and need for early cesarean delivery. 3