What is the management of placenta previa during pregnancy?

Management of Placenta Previa During Pregnancy

Placenta previa requires transvaginal ultrasound for diagnosis, avoidance of digital examination, activity modification after 28 weeks, screening for placenta accreta spectrum in high-risk patients, and planned cesarean delivery at 34-35 weeks at a tertiary care facility with multidisciplinary team and blood bank capabilities. 1, 2, 3

Diagnosis and Initial Assessment

Diagnostic approach:

• Transvaginal ultrasound is the gold standard with 90.7% sensitivity and 96.9% specificity, performed after initial transabdominal screening 2, 3
• Measure the distance from the leading placental edge to the internal cervical os; overlap ≥15 mm at mid-trimester predicts persistence at delivery 2, 3
• Never perform digital pelvic examination until placenta previa is excluded, as this can trigger life-threatening hemorrhage 1, 2, 3
• Use Doppler ultrasound to identify vasa previa and assess placental blood flow patterns 3

Follow-up imaging protocol:

• Schedule ultrasounds at 18-20 weeks, 28-30 weeks, and 32-34 weeks to assess for resolution, placental location, and possible bladder invasion 3
• Most cases diagnosed early in pregnancy resolve by 28 weeks as the lower uterine segment develops 1, 3

Risk Stratification for Placenta Accreta Spectrum

Critical assessment required:

• All women with placenta previa AND prior cesarean deliveries must be evaluated for placenta accreta spectrum disorder, which dramatically increases morbidity 1, 2, 3
• Risk increases exponentially: 7-fold after one prior cesarean to 56-fold after three cesarean deliveries 1, 2, 3
• 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, 2, 3
• MRI may be helpful when ultrasound findings are concerning for accreta, particularly for posterior placenta previa or suspected placenta percreta 1, 3

Common pitfall: Failure to diagnose placenta accreta spectrum in women with placenta previa and prior cesarean deliveries can lead to catastrophic hemorrhage 2, 3

Antepartum Management

Activity restrictions:

• Women with asymptomatic placenta previa can continue moderate-to-vigorous physical activity before 28 weeks 1, 2, 3
• After 28 weeks, avoid moderate-to-vigorous physical activity but maintain activities of daily living and low-intensity activity such as walking 1, 2, 3
• Hospitalization is required for active bleeding 1, 2, 3

Anemia optimization:

• Maximize hemoglobin values during pregnancy by treating anemia with oral or intravenous iron as needed to prepare for potential hemorrhage at delivery 1, 3

Delivery Planning and Timing

Timing of delivery:

• Planned cesarean delivery at 34 0/7 to 35 6/7 weeks of gestation for uncomplicated placenta previa, balancing neonatal complications against increased maternal bleeding risk after 36 weeks 1, 2, 3
• Do not delay beyond 36 0/7 weeks, as approximately 50% of women with placenta accreta spectrum beyond 36 weeks require emergent delivery for hemorrhage 1, 2, 3
• Earlier delivery is required for persistent bleeding, preeclampsia, labor, rupture of membranes, or fetal compromise 2
• Administer antenatal corticosteroids when delivery is anticipated before 37 0/7 weeks 2, 3

Delivery location:

• Delivery must occur at a level III or IV maternal care facility with adequate blood banking facilities and multidisciplinary expertise 1, 2, 3
• Required team members include maternal-fetal medicine subspecialists, pelvic surgeons, urologists, interventional radiologists, obstetric anesthesiologists, and neonatologists 2, 3
• Blood bank must be capable of employing massive transfusion protocols 2, 3
• Notify blood bank in advance due to frequent need for large-volume blood transfusion 1, 3

Preoperative coordination:

• Essential coordination with anesthesiology, maternal-fetal medicine, neonatology, and expert pelvic surgeons 1, 2, 3
• If placenta previa persists at 28-30 week ultrasound, refer early to tertiary care facility 3

Intraoperative Management

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, 3
• For suspected bladder involvement, consider ureteric stent placement and collaboration with urologic surgeons 1, 3

Management of 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, as this causes profuse hemorrhage 1, 2, 3
• Cesarean hysterectomy may be necessary for placenta accreta spectrum 1, 2

Hemorrhage Management

Transfusion protocol:

• Activate massive transfusion protocol early rather than late 2, 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, 3
• Baseline laboratory assessment at bleeding initiation should include platelet count, prothrombin time, partial thromboplastin time, and fibrinogen levels 1, 3
• Consider tranexamic acid to reduce blood loss 2, 3

Intraoperative considerations:

• Keep patients warm (>36°C) during surgery as clotting factors function poorly at lower temperatures 1, 3
• Re-dose prophylactic antibiotics if blood loss ≥1,500 ml 1, 3

Common pitfall: Delayed activation of massive transfusion protocol can worsen outcomes 2

Postoperative Care

Monitoring:

• Intensive hemodynamic monitoring in the early postoperative period is recommended, often best provided in an intensive care unit setting 1, 2, 3
• Close monitoring of volume status, urine output, blood loss, and hemodynamics is essential 1, 2, 3
• Maintain a low threshold for reoperation if ongoing bleeding is suspected 1, 2, 3

Follow-up:

• Ensure adequate iron supplementation and follow-up of hemoglobin levels if significant blood loss occurred 1, 3