Ultrasound signs in the diagnosis of placental anomalies: placenta accreta at the level of the uterine scar
Oana-Denisa Bălălău1,2, Adina-Teodora Corbu1,2, Cristian Bălălău2, Romina-Marina Sima1,2, Liana Pleș1,2, Anca-Daniela Stănescu1,2
1St. Ioan Clinical Emergency Hospital – Bucur Maternity, Bucharest, Romania
2Carol Davila University of Medicine and Pharmacy, Bucharest, Romania
Introduction. The incidence of Caesarian section has increased remarkably in recent years, which also leads to the increased maternal and fetal morbidity due to the complications that occur after the changes in the myometrial structure of the uterine scar. Placental anomalies with an increased risk for both the mother and the fetus are known under the heading of AIP (abnormally invasive placentation). Approximately 80% of the cases of placental anomalies are associated with a history of Caesarian delivery, curettage or myomectomies with the opening of the uterine cavity.
Aims and scope. The present paper aims at highlighting the current techniques of diagnosing placental abnormalities from the first trimester of pregnancy. Several studies in the specialty literature have been evaluated, those published in the last 5 years (2015-2019) on the PubMed platform, the results being presented in the form of a review.
Results. In 2018, Pagani et al. conducted a meta-analysis on 20 studies in the specialty literature. The current techniques used to diagnose placental abnormalities are abdominal and transvaginal ultrasound and Doppler ultrasound. A number of 7 studies (721 cases) used ultrasound to diagnose abnormalities. The identification of the degree of invasion was performed with a specificity of 97.1% - placenta accreta, 98.4% - placenta increta, 98.9% - placenta percreta and a sensitivity of 90.6%, 93% and 81.2% respectively. The main signs evidenced upon ultrasound, which are currently used by most authors in specialized studies are: the loss/ the interruption of the hypoechoic area at the level of the myometrium under the placental bed, placental gaps (which may exhibit turbulent blood flow), the interruption of the hyperechoic line represented by the posterior bladder wall and the uterine serous membrane at this level, the thinning of the myometrium (reaching < 1mm), the presence of an exophytic formation which exceeds the uterine serous membrane, infiltrating into the urinary bladder. The echo Doppler images reveal: blood flow at the level of the placental gaps, intense vascularization in the subplacental area and vesicouterine hyper-vascularization. In a paper published in 2018, Cali et al. highlighted the importance of identifying these ultrasound signs from the first trimester of pregnancy. The accuracy of diagnosing AIP in the first trimester is low compared to the 2nd and 3rd trimesters: the loss of the hypoechoic area 84.3% vs. 92.4%, the presence of placental gaps 78.3% vs. 100%, the interruption of the hyperechoic line at the level of the urinary bladder 75.9% vs. 93.3%, vesicouterine hyper-vascularization 50.6% vs. 81%.
Conclusions. The importance of making an accurate diagnosis, as early as possible, of a placental anomaly is vital. The close monitoring of the pregnant woman, with serial ultrasounds performed quarterly, which should follow the signs indicated until so far in the specialized studies, as well as the preparation of a multidisciplinary operative team increases the probability of giving birth to a living new born baby, as well as the chance of preserving maternal fertility.