## Placenta Previa: Management and Diagnosis ### Key Diagnostic and Management Principles **Key Point:** Transvaginal ultrasound is NOT contraindicated in placenta previa and is actually the gold standard for accurate assessment of placental location relative to the internal cervical os. The myth that it may cause hemorrhage is unfounded and has been dispelled by multiple studies. ### Correct Management Approach **High-Yield:** In a hemodynamically stable patient with placenta previa and cessation of bleeding, expectant (conservative) management with hospitalization is the standard of care until fetal maturity or recurrent bleeding occurs. **Clinical Pearl:** Vaginal delivery is safe and acceptable if the lower edge of the placenta is >2 cm from the internal cervical os (complete previa or marginal previa with adequate clearance). This allows vaginal delivery at term without increased hemorrhage risk. ### Risk Factors for Placenta Previa | Risk Factor | Mechanism | |---|---| | Advanced maternal age (>35 years) | Endometrial atrophy and poor vascularity | | Multiparity | Cumulative endometrial damage | | Prior uterine curettage/D&C | Endometrial scarring and poor decidualization | | Prior cesarean section | Placental implantation over scar tissue | | Smoking | Impaired placental growth and positioning | | Cocaine use | Placental ischemia and abnormal implantation | | Assisted reproductive techniques | Altered endometrial receptivity | ### Why Transvaginal Ultrasound Is Safe 1. No mechanical trauma to the placenta occurs with gentle probe placement 2. The probe does not enter the cervical canal in placenta previa 3. Provides superior visualization of the relationship between placenta and internal os 4. Reduces false-positive diagnosis of previa compared to transabdominal ultrasound alone **Warning:** The historical concern about transvaginal ultrasound causing hemorrhage in placenta previa is a common misconception that persists in clinical practice but is NOT supported by evidence. [cite:Williams Obstetrics 26e Ch 34]
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