OP27.04: Comparison of transabdominal ultrasound (US) versus transvaginal US in the accurate prenatal assessment of abnormally invasive placenta (AIP)

Abstract

To study if adding transvaginal Ultrasound (TVS) exam using grey scale and Doppler parameters to transabdominal ultrasound TAS improves the accuracy of prenatal diagnosis of Abnormally invasive placenta AIP. Pregnant women with persistent placenta previa after 28 weeks' gestation attending the antenatal care at Cairo University Obstetrics department were prospectively included. History taking included number of prior Caesarean sections. All patients underwent TAS & TVS using gray-scale & colour Doppler by two different senior operators, assessing the following criteria: Loss of the retro placental clear zone, thinning or interruption of the uterine serosa–bladder wall interface, myometrial thickness<1mm, turbulent placental lacunae with high velocity flow (>15 cm/s), increased vascularity of the uterine serosa–bladder wall interface. Data collection included full surgical management. Fifty patients underwent US evaluation and were delivered by Caesarean section at Cairo University hospital. The mean age of the patients was 32.6, mean number of previous Caesarean sections was 3. Forty three cases with abnormal invasion of placenta were correctly diagnosed before delivery all of whom proceeded directly to Caesarean hysterectomy & AIP was confirmed by histopathology. There was good agreement between TAS & TVS in diagnosing AIP however the presence of abnormal lacunae & loss of the retro placental clear zone as seen by TVS had the highest sensitivity, specificity NPV, PPV & accuracy; 93.0%, 57.1%, PPV 93.0%, NPV 57.1%, accuracy 88.0% & 74.4%, 85.7%,97.0%, 35.3%, 76.0% respectively. There was no statistical difference in diagnostic ability of US criteria when comparing TAS to TVS except for Loss of the retro placental clear zone which was significantly better seen by TVS (0.003). AIP can be diagnosed with good accuracy antenatal using TAS, adding TVS could aid in diagnostic accuracy especially when retro placental clear zone & abnormal lacunae are seen.