Background: The correct diagnosis of placenta previa is a crucial task to prevent associated complications. Ultrasound is considered the gold standard technique. However, the appropriate technique, with 100% sensitivity is not yet determined.
The aim of the work: The current study aimed to compare the transabdominal 3D versus transvaginal 2D ultrasound in the assessment of placental invasion in women with placenta previa with previous uterine scar.
Patients and Methods: The study included sixty patients with confirmed ultrasound placenta previa. Each patient was evaluated by the full history taking, clinical examination. Finally, ultrasound was performed for all women. The placenta was examined while the bladder is partially full [about 300 ml] for adequate visualization and precise localization. A complete US scan had been performed and included 2D vaginal ultrasound, and 3D abdominal ultrasound. At delivery, intraoperative definitive diagnosis of abnormally invasive placenta was made. Data compared to the previous ultrasound diagnosis.
Results: The hematocrit value was significantly decreased after the operation compared to preoperative values [27.16 ± 2.51 vs 30.92 ± 2.78, respectively, p = 0.024]. The sensitivity of 3D transabdominal ultrasound was 53.3%, 65.0%, 88.3% and 73.3% for the detection of retroplacental clear zone, myometrial thinning, uterovesical vascularity and bladder wall interruption, successively. Otherwise, the 2D transvaginal ultrasound sensitivity was 75%, 71.6%, 83.3% and 7.7% for the same conditions. The 3D transabdominal US was 72.5% sensitive, 90% specific, 84.1% PPV, 60.9% NPV and 76.7% accuracy. The 2D transvaginal US revealed 87.4% sensitivity, 73.7% specificity, 93.3% PPV, 41.6% NPV and 89.3% accuracy.
Conclusion: 2D vaginal ultrasound is more sensitive compared to the 3-D abdominal sonography in detecting placenta previa. However, the 3D transabdominal US higher sensitivity in detecting some radiological signs of this lesions like uterovesical vascularity.