A novel classification system for cesarean scar pregnancy based on contrast-enhanced ultrasound patterns reduces invasive surgery and surgical risk: a prospective cohort study

Preoperative risk assessment of cesarean scar pregnancy (CSP) in early pregnancy mainly relies on two-dimensional ultrasound classification; however, it fails to fully reflect blood supply and myometrial invasion, thereby limiting surgical decision-making. This study aims to investigate whether a novel classification based on contrast-enhanced ultrasound (CEUS) can more accurately identify high-risk cases and reduce unnecessary invasive surgical procedures.

A prospective cohort study design was adopted. A total of 128 patients diagnosed with CSP according to the 2016 Expert Consensus were enrolled from Department of Obstetrics and Gynecology of Yingshang People’s Hospital during August 2021 and January 2026. The 2016 consensus classification categorized CSP into Types Ⅰ to Ⅲ mainly based on the relationship between the gestational sac and cesarean scar location as well as the residual myometrial thickness between the sac and the bladder. Our CEUS-based classification was developed based on the positional relationship between the peak “early and hyper-enhanced” trophoblastic perfusion area within 2 min after contrast injection and the scar myometrium, as well as the morphology of gestational tissues. Thus, the CSP cases were classified into 7 subtypes: Ⅰa, Ⅰb, Ⅰc, Ⅱa, Ⅱb, Ⅲa, and Ⅲb, and planned surgical approaches were formulated accordingly. Weighted Kappa test was used to evaluate the consistency of recommended surgical approaches between the 2 systems, and Pearson’s χ² test was employed to compare the distribution of recommendations. The rate and direction (downgrading vs upgrading) of CEUS-induced changes in classification and surgical strategy were calculated with 95%confidence intervals (95%CIs).

The 2016 Expert Consensus identified 60 cases (46.9%) as Type Ⅰ, 43 (33.6%) as Type Ⅱ, and 25 (19.5%) as Type Ⅲ. The CEUS classification identified 35 Type Ia cases (27.3%), 26 Type Ib (20.3%), 10 Type Ⅰ c (7.8%), 35 Type Ⅱ a (27.3%), 11 Type Ⅱ b (8.6%), 2 Type Ⅲ a (1.6%), and 9 Type Ⅲ b (7.0%). CEUS reclassification changed the classification in 55 cases (43.0%) and the final surgical approach in 56 cases (43.7%, 95%CI: 35.4% to 52.0%), including 47 downgraded (36.7%, 95%CI: 28.5% to 44.9%) and 9 upgraded cases (7.0%, 95%CI: 3.1% to 10.9%). Compared with the 2016 Consensus, CEUS-based classification reduced the planned proportion of invasive scar repair from 53.1% (68/128) to 17.2% (22/128) and increased the ratio of minimally invasive dilation and curettage (D&C)/hysteroscopic strategies from 46.9% (60/128) to 82.8% (106/128). The weighted Kappa was 0.582 (95%CI: 0.441 to 0.723), indicating moderate consistency, and Pearson’s χ² was 23.44 (df=1, P<0.001), indicating a significant difference in recommendation distribution.

Our new CEUS pattern-based classification improves preoperative risk stratification beyond conventional morphologic assessment, markedly reduces the planned proportion of invasive scar repair, and retains the ability to identify high-risk cases. This system may provide imaging evidence for individualized and minimally invasive management of early CSP.