Management of Placenta Previa

Diagnostic Approach

• Transvaginal ultrasound is the gold standard for diagnosing placenta previa with 90.7% sensitivity and 96.9% specificity, and should be used after initial transabdominal ultrasound screening 1, 2
• The distance from the leading placental margin to the internal cervical os should be measured, with overlap of ≥15 mm at mid-trimester predicting persistence at delivery 1
• Doppler ultrasound should be used to identify vasa previa and assess placental blood flow patterns, particularly for posterior placenta previa or suspected placenta percreta 2, 3
• Digital pelvic examination must be avoided until placenta previa has been excluded, as it can trigger life-threatening hemorrhage 4, 1

Risk Stratification for Placenta Accreta Spectrum

• All women with placenta previa and prior cesarean deliveries must be evaluated for placenta accreta spectrum disorder, which increases morbidity, with a 7-fold increase after one prior cesarean to 56-fold after three cesarean deliveries 4, 1
• Additional risk factors for placenta accreta spectrum include advanced maternal age, high parity, prior uterine surgery, prior postpartum hemorrhage, Asherman syndrome, uterine anomalies, smoking, hypertension, and in vitro fertilization 4, 1

Antepartum Activity Restrictions

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

Anemia Optimization

• Hemoglobin values should be maximized during pregnancy by treating anemia with oral or intravenous iron as needed to prepare for potential hemorrhage at delivery 4, 1

Delivery Planning and Timing

• Cesarean delivery should be planned 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 4, 1
• 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 4, 1
• Antenatal corticosteroids should be administered when delivery is anticipated before 37 0/7 weeks 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, including maternal-fetal medicine subspecialists, pelvic surgeons, urologists, interventional radiologists, obstetric anesthesiologists, neonatologists, and blood bank capabilities 4, 1
• The blood bank should be notified in advance due to the frequent need for large-volume blood transfusion 4, 1

Intraoperative Management

• Preoperative coordination with anesthesiology, maternal-fetal medicine, neonatology, and expert pelvic surgeons is essential 4, 1
• The uterine incision should be made away from the placenta when possible, and consideration should be given to dorsal lithotomy positioning and inspection of the uterus after peritoneal entry 4, 1
• For suspected bladder involvement, ureteric stent placement and collaboration with urologic surgeons should be considered 4, 5

Hemorrhage Management

• Massive transfusion protocol should be activated early rather than late, with transfusion of packed red blood cells, fresh frozen plasma, and platelets in a 1:1:1 to 1:2:4 ratio for acute hemorrhage 4, 1
• Patients should be kept warm (>36°C) during surgery, and prophylactic antibiotics should be re-dosed if blood loss ≥1,500 ml 4
• Baseline laboratory assessment at bleeding initiation should include platelet count, prothrombin time, partial thromboplastin time, and fibrinogen levels 4
• Tranexamic acid should be considered to reduce blood loss 1

Postoperative Care

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

Management of Placenta Previa

Follow-Up Imaging Protocol

• The American College of Obstetricians and Gynecologists recommends scheduling 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 6, 7, 8
• This protocol allows assessment of whether the placenta migrates away from the cervical os as the lower uterine segment develops, with a high likelihood of resolution by 28 weeks 6, 7

Planning for Persistent Placenta Previa

• The American College of Obstetricians and Gynecologists advises early referral to a level III or IV maternal care facility with multidisciplinary expertise, including maternal-fetal medicine subspecialists, if placenta previa persists at the 28-30 week ultrasound 6, 7

Management of Placenta Previa with Hemodynamic Instability

Rationale for Immediate Delivery Planning

• Blood transfusion alone is supportive care, not definitive management for patients with placenta previa, and may be necessary but does not address the underlying problem of ongoing bleeding risk, according to the American College of Obstetricians and Gynecologists 9

Optimal Management Algorithm

• Immediate stabilization and administration of antenatal corticosteroids, such as intramuscular dexamethasone, is necessary for patients with placenta previa and hemodynamic instability, as recommended by the American College of Obstetricians and Gynecologists 9

Ultrasound Evaluation in Placenta Previa (Cited Evidence)

Diagnostic Imaging Recommendations

• The American College of Radiology states that transvaginal ultrasound is safe in pregnant patients with placenta previa and offers superior visualization of the cervix and lower uterine segment compared with a transabdominal approach. 10

• According to the American College of Radiology, a comprehensive ultrasound assessment should include Doppler evaluation to rule out vasa previa, a condition that can cause fetal exsanguination if undetected. 10

• The American College of Radiology notes that measuring lower uterine segment thickness by ultrasound is important; a thickness < 2.5 mm indicates an increased risk of uterine rupture, particularly in patients with a prior cesarean delivery. 10

Risk Stratification Findings

• Ultrasound can identify placental abruption in up to 50 % of cases, and detection of abruption is associated with worse perinatal outcomes. 10

• A short cervical length identified on ultrasound, when accompanied by vaginal bleeding, significantly raises the risk of preterm delivery. 10