Integration of first‐trimester assessment in the ultrasound staging of placenta accreta spectrum disorders

OBJECTIVE: To explore the role of early first trimester ultrasound at 5-7 postmenstrual weeks of gestation in predicting sonographic staging of placenta accreta spectrum (PAS) and to elucidate whether integrating first trimester assessment with ultrasound staging of PAS can predict surgical outcome in women at risk for PAS. METHODS: Secondary analysis of prospectively collected data of women who had at least one previous caesarean delivery (CD) or uterine surgery and placenta previa for whom early (5-7 weeks of gestation) ultrasound images could be retrieved. The relationship between gestational sac position and prior CD scar was assessed using classifications by Cali et al. (cross-over COS), Kaelin Agten et al. ("on the scar" vs "in the niche" implantation) and Timor-Tritsch et al. ("above the line" vs "below the line" implantation) by two different examiners blinded to the final diagnosis and clinical outcome. Primary aim of the study was to explore the strength of association and predictive accuracy of first trimester ultrasound in predicting PAS stage. Secondary aim was to elucidate whether integration of first trimester ultrasound with PAS staging can predict surgical outcome. Logistic regression and area under the curve analyses were used to analyse the data. RESULTS: One hundred and eighty-seven women were included. Of these ,79.6% (95% CI 67.1-88.2) had COS1, 94.4% (95% CI 84.9-98.1) "in the niche" and 92.6% (95% CI 82.4-97.1) "below the line" implantation confirmed to be affected by PAS3 in the third trimester of pregnancy. On multivariate logistic regression analysis, COS1 (OR: 7.9 (95% CI 4.0-15.5; p<0.001), "in the niche" (OR: 29.1, 95% CI 8.1-104; p<0.001) and "below the line" (OR: 38.1, 95% CI 12.1-121; p<0.001) implantations, however, neither parity (p= 0.4), nor the number of prior CDs (p= 0.5) were independently associated with PAS3. When translating these figures in a diagnostic model, either COS1 (AUC: 0.94, 95% CI 0.91-0.97), or implantation "in the niche" (AUC: 0.92, 95% CI 0.89-0.96) or "below the line" (AUC: 0.92, 95% CI 0.88-0.96) had a high predictive accuracy for PAS3. Adverse surgical outcome was more common in women with COS1 (p<0.001), implantation "in the niche" (p<0.001) and "below the line" (p<0.001) then those without them.) On multivariate logistic regression analysis, ultrasound diagnosis of PAS3 (OR: 4.3, 95% CI 2.1-17.3), COS1 (OR: 7.9, 95% CI 4.0-15.5; p<0.001), "in the niche" (OR: 29.1, 95% CI 8.1-104; p<0.001) and "below the line" (OR: 7.9, 95% CI 4.0-15.5; p<0.001) implantations were independently associated with adverse surgical outcome. When combining the three imaging methods, we identified, an area we call "high-risk-for-PAS Triangle" which may enable an easy visual perception and application of the three methods to prognosticate the risk for CSP and PAS, although it requires validation in further large prospective studies. CONCLUSION: Early first trimester sonographic assessment of pregnancies after CDs can reliably predict ultrasound staging of possible PAS. Integrating first with second and third trimester ultrasound can stratify surgical risk of women affected by PAS. This article is protected by copyright. All rights reserved.