Trimester‐specific diagnostic accuracy of ultrasound for detection of placenta accreta spectrum: systematic review and meta‐analysis

ABSTRACT Background This study aimed to assess the diagnostic accuracy of ultrasound for detecting placenta accreta spectrum (PAS) during the first trimester of pregnancy and compare it with the accuracy of second and third trimester ultrasound in pregnancies at risk for PAS. Methods PubMed, Embase, and Web of Science, databases were searched to identify relevant studies published from inception until March 10th, 2023. Inclusion criteria were all studies, including cohort, case‐control, or cross‐sectional studies, that evaluated the diagnostic accuracy of first trimester ultrasound performed prior to 14 weeks (first trimester) or after 14 weeks of gestation (second/third trimester) for diagnosis of PAS in pregnancies with clinical risk factors. The primary outcome was to assess the diagnostic accuracy of ultrasound in detecting PAS in the first trimester, and to compare it with the accuracy of ultrasound in the second and third trimesters. The secondary outcome was to evaluate the diagnostic accuracy of each ultrasonographic marker individually across the trimesters of pregnancy. Reference standard was PAS confirmed at pathological or surgical examination. The potential of ultrasound and different ultrasound signs to detect PAS was assessed by computing summary estimates of sensitivity, specificity, diagnostic odds ratio (DOR) and positive (LR+) and negative (LR‐) likelihood ratios. Results A total of 37 studies including 5,764 pregnancies at risk of PAS, with 1,348 cases of confirmed PAS, were included in our analysis. The meta‐analysis yielded a sensitivity of 86% (95% CI: 78%, 92%) and specificity of 63% (95% CI: 55%, 70%) during the 1st trimester, while the sensitivity was 88% (95% CI: 84%, 91%) and specificity was 92% (95% CI: 85%, 96%) during the 2nd/3rd trimester. Regarding ultrasonographic markers examined in the 1st trimester, lower uterine hypervascularity exhibited the highest sensitivity of 97% (95% CI: 19%, 100%), and uterovesical interface irregularity demonstrated the highest specificity of 99% (95% CI: 96%, 100%). However, in the 2nd/3rd trimester, loss of clear zone had the highest sensitivity of 80% (95% CI: 72%, 86%), while uterovesical interface irregularity exhibited the highest specificity of 99% (95% CI: 97%, 100%). Conclusion First trimester ultrasound has similar accuracy to second and third trimester ultrasound for the diagnosis of PAS. Routine first trimester ultrasound screening for patients at high risk of PAS may improve detection rates and allow earlier referral to tertiary care centers for pregnancy management. This article is protected by copyright. All rights reserved.