The Predictive Accuracy of Anogenital Distance and Genital Tubercle Angle for First-Trimester Fetal Sex Determination.

BACKGROUND

Early identification of fetal gender is crucial for managing gender-linked genetic disorders. This study aimed to evaluate the predictive performance of anogenital distance (AGD) and genital tubercle angle (GTA) for fetal sex determination during the first trimester.

METHODS

A multicenter retrospective cohort study was conducted on 312 fetal cases between 11 and 13 + 6 weeks of gestation from two tertiary hospitals. AGD and GTA measurements were taken from midsagittal plane images using ultrasound, with intra- and inter-reader reproducibility assessed. Binomial logistic regression and ROC curve analysis were employed to determine the diagnostic performance and optimal cutoff points.

RESULTS

AGD had a mean of 7.16 mm in male fetuses and 4.42 mm in female fetuses, with a sensitivity of 88.8%, specificity of 94.4%, and an area under the ROC curve (AUC) of 0.931 (95% CI: 0.899-0.962) using 5.74 mm as a cutoff point. For GTA, the mean was 35.90 degrees in males and 21.57 degrees in females, with a sensitivity of 92%, specificity of 84.7%, and an AUC of 0.932 (95% CI: 0.904-0.961) using 28.32 degrees as a cutoff point. The reproducibility results were excellent for AGD (intra-operator ICC = 0.938, inter-operator ICC = 0.871) and moderate for GTA (intra-operator ICC = 0.895, inter-operator ICC = 0.695).

CONCLUSIONS

The findings suggest that AGD and GTA are reliable markers for early fetal sex determination, with AGD showing higher reproducibility. The findings highlight the feasibility and accuracy of these non-invasive sonographic markers and their potential usefulness in guiding timely interventions and enhancing the management of gender-linked genetic conditions.