Management of Placenta Previa

Diagnosis and Initial Assessment

The American College of Radiology recommends transvaginal ultrasound as the gold standard for diagnosing placenta previa, with sensitivity of 90.7% and specificity of 96.9% 1
Transabdominal ultrasound should be used as initial screening, followed by transvaginal ultrasound for definitive assessment 2, 1
The distance from the leading placental margin to the internal cervical os should be measured, with overlap of 15 mm or more at mid-trimester predicting persistence at delivery 2
Placenta previa occurs when the placenta overlies the internal cervical os, affecting approximately 0.4% of third-trimester pregnancies 1

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

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

Planned cesarean delivery at 34 0/7 to 35 6/7 weeks of gestation is recommended for uncomplicated placenta previa 1
Earlier delivery is required for persistent bleeding, preeclampsia, labor, rupture of membranes, or fetal compromise 1

The uterine incision should be made away from the placenta when possible 1
Forced placental removal should never be attempted, as this causes profuse hemorrhage 1
Tranexamic acid may be considered to reduce blood loss 3

Intensive hemodynamic monitoring is recommended 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 is essential 1
A low threshold for reoperation should be maintained if ongoing bleeding is suspected 1

Failure to diagnose placenta accreta spectrum in women with placenta previa and prior cesarean deliveries can lead to catastrophic hemorrhage 1
Digital examination without excluding placenta previa can trigger life-threatening bleeding 1
Delayed activation of massive transfusion protocol can worsen outcomes; activation should occur early rather than late 3