Gestational sac ellipticity index measured at ≤ 7 weeks' gestation as a predictor of first-trimester embryonic
1Department of Ultrasound, Chengdu Qingbaijiang Maternal and Child Heath Care Hospital, Chengdu, Sichuan, China.
Purpose:
To evaluate the predictive value of the Gestational Sac Ellipticity Index (EI), a quantitative measure of sac irregularity, for subsequent early embryonic demise within the first trimester, when measured at or before 7 weeks of gestation.
Methods:
This single-center retrospective cohort study included 340 singleton pregnancies with initial transvaginal ultrasound at ≤ 7 weeks. The EI was calculated as 1 - (short axis/long axis). Propensity score matching (PSM) was used to balance baseline characteristics. Univariate and multivariate logistic regression, receiver operating characteristic (ROC) analysis, decision curve analysis (DCA), and net reclassification improvement (NRI) were performed to assess the predictive performance and incremental value of EI.
Results:
After PSM, 85 embryonic demise cases were matched with 85 continued pregnancies. The EI was significantly higher in the demise group (median 0.35 vs. 0.18, p < 0.001). Each 0.1 increase in EI was associated with an adjusted odds ratio of 1.78 (95% CI: 1.25-2.54) for demise. The area under the ROC curve (AUC) for EI was 0.794 (95% CI: 0.728-0.860). An optimal cut-off value of 0.275 yielded a sensitivity of 81.2% and specificity of 67.1% for predicting embryonic demise. Adding EI to a baseline model (maternal age, mean sac diameter, crown-rump length, cardiac activity) significantly improved the AUC from 0.856 to 0.884 (p = 0.009), with NRI = 0.312 (p = 0.002). Subgroup analyses confirmed EI's predictive value even when fetal cardiac activity was present and at earlier gestational ages.
Conclusion:
In this cohort, the Gestational Sac Ellipticity Index, when measured at or before 7 weeks, was found to be an independent predictor of first-trimester embryonic demise and showed incremental value over existing markers. An EI cut-off of 0.275 provided a basis for risk stratification, suggesting its potential for further investigation as a tool in early pregnancy assessment protocols, pending external validation.
