Early fetal sex determination: the predictive value of anogenital distance and fetal heart rate in first-trimester ultrasound.

Background: Determining fetal sex during the early stages can help identify potential x-linked disorders and predict pregnancy complications and outcomes related to fetal sex. Few studies have evaluated the use of anogenital distance (AGD) and fetal heart rate (FHR) as sonographic markers for predicting fetal sex in the first trimester. Therefore, this study aimed to predict fetal sex by measuring AGD and FHR using ultrasound in the first trimester.

Methods: This cross-sectional study was conducted at Shahid Beheshti Hospital, Isfahan City, in 2022-2023. Ultrasound scans of 143 singleton pregnancies between 11 and 13 plus 6 gestational weeks and their fetal sex at birth were collected. The exact age of pregnancy was determined by measuring crown-rump length (CRL). The diagnostic value of AGD and FHR in predicting fetal sex was evaluated using receiver operating characteristic (ROC) curve analysis, and indicators such as sensitivity, specificity, positive and negative predictive value, and the area under the curve (AUC) were reported.

Results: A total of 143 pregnant women with the mean age of 31.08 ± 5.26 years were entered to our study. The mean CRL and FHR in male and female fetuses were not significantly associated with fetal sex (P > 0.001). However, AGD was significantly higher in male fetuses than in female fetuses (P < 0.001). Moreover, we found that AGD at the cut-off point of 4.2 mm had a significant diagnostic value in predicting male sex (AUC = 0.792; P < 0.001).

Conclusion: Our study demonstrated that AGD measurement, unlike FHR and CRL, could be a valuable procedure for predicting fetal sex.