What are the management guidelines for placenta previa?

Management Guidelines for Placenta Previa

Deliver all women with placenta previa by planned cesarean delivery at 34 0/7 to 35 6/7 weeks of gestation in stable patients, with delivery taking place at an institution with adequate blood banking facilities and multidisciplinary expertise. 1

Diagnosis and Initial Assessment

Diagnostic Approach

• Transvaginal ultrasound is the gold standard for diagnosing placenta previa, with sensitivity of 90.7% and specificity of 96.9% 1
• Begin with transabdominal ultrasound as initial screening, followed by transvaginal ultrasound for definitive assessment 2, 1
• Never perform digital pelvic examination until placenta previa has been excluded, as this can trigger catastrophic hemorrhage 1
• Measure the distance from the leading placental margin to the internal cervical os; overlap of 15 mm or more at mid-trimester predicts persistence at delivery 2

Classification and Natural History

• Placenta previa occurs when the placenta overlies the internal cervical os, affecting approximately 0.4% of third-trimester pregnancies 1
• While common in early pregnancy (42.3% at 11-14 weeks), most cases resolve by 28 weeks 1
• Repeat ultrasound evaluation is essential for cases with significant placental overlap in the second trimester 2

Risk Stratification for Placenta Accreta Spectrum

Critical Risk Assessment

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

Antepartum Management

Activity Restrictions

• Before 28 weeks: Women with asymptomatic placenta previa can continue moderate-to-vigorous physical activity 1
• After 28 weeks: Avoid moderate-to-vigorous physical activity but maintain activities of daily living and low-intensity activity such as walking 1
• Hospitalize women with active bleeding 1

Medical Optimization

• Optimize hemoglobin values throughout pregnancy; treat anemia with oral or intravenous iron as needed 1
• Administer antenatal corticosteroids when delivery is anticipated before 37 0/7 weeks 1
• Establish baseline laboratory assessment including platelet count, prothrombin time, partial thromboplastin time, and fibrinogen levels 1

Delivery Planning and Timing

Optimal Timing

• Planned cesarean delivery at 34 0/7 to 35 6/7 weeks of gestation for uncomplicated placenta previa 1
• Do not wait beyond 36 0/7 weeks, as approximately 50% of women with placenta accreta spectrum beyond 36 weeks require emergent delivery for hemorrhage 1
• Earlier delivery is required for persistent bleeding, preeclampsia, labor, rupture of membranes, or fetal compromise 1

Preoperative Coordination

• Notify and coordinate with anesthesiology, maternal-fetal medicine, neonatology, and expert pelvic surgeons before delivery 1
• Alert blood bank in advance due to frequent need for large-volume transfusion 1
• For suspected bladder involvement, arrange ureteric stent placement and urologic surgeon collaboration 1
• Prepare massive transfusion protocol with 1:1:1 to 1:2:4 ratio of packed red blood cells:fresh frozen plasma:platelets 1

Intraoperative Management

Surgical Technique

• Position patient in dorsal lithotomy to allow vaginal access and optimal surgical visualization 1
• Inspect the uterus after peritoneal entry to determine placental location and optimize uterine incision placement 1
• Make the uterine incision away from the placenta when possible 1
• After fetal delivery, 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

Management of Hemorrhage

• Maintain patient temperature above 36°C, as clotting factors function poorly at lower temperatures 1
• Re-dose prophylactic antibiotics if blood loss exceeds 1,500 mL 1
• Transfuse packed red blood cells, fresh frozen plasma, and platelets in fixed ratio during acute hemorrhage 1
• Consider tranexamic acid to reduce blood loss 3

Placenta Accreta Spectrum

• Cesarean hysterectomy is necessary in the majority of women with significant placenta accreta 1, 4
• Cell salvage technology should be available when possible 3

Postoperative Care

Immediate Monitoring

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

Complications Surveillance

• Monitor for renal failure, liver failure, infection, unrecognized injuries, pulmonary edema, and disseminated intravascular coagulation 3
• Be vigilant for Sheehan syndrome (postpartum pituitary necrosis) in cases with significant hypoperfusion 3
• Ensure adequate iron supplementation and follow-up of hemoglobin levels if significant blood loss occurred 1

Critical Pitfalls to Avoid

• Failure to diagnose placenta accreta spectrum in women with placenta previa and prior cesarean deliveries leads to catastrophic hemorrhage 1
• Digital examination without excluding placenta previa can trigger life-threatening bleeding 1
• Delayed activation of massive transfusion protocol worsens outcomes; activate early rather than late 3
• Attempting vaginal delivery with complete placenta previa is contraindicated 4
• Transfer to higher level of care should occur if diagnosis is made at a center without appropriate resources, assuming maternal and fetal stability 3