Anogenital Distance for Detection of Fetal Sex in First Trimester

Abstract

Background: The determination of fetal sex in the first trimester has significant implications, not only for familial curiosity but more  critically in sex-linked genetic disorders. Traditional methods range from invasive procedures with associated risks to non-invasive  techniques that may lack universal accessibility or come with high costs. Ultrasonography in the second trimester, though effective, offers  a delayed resolution that may not be ideal for early intervention in cases of sex-linked diseases.

Objective: This study aimed to  assess the utility of anogenital distance (AGD) measurements in the first trimester as a reliable, non-invasive predictor of fetal sex,  thereby facilitating earlier diagnosis and management of sex-linked conditions.

Methods: This prospective cohort study was conducted  at Benha University Hospitals' Feto-maternal Unit, 245 pregnant women within 11-13 weeks +6 days of gestation were included. The AGD  was measured via ultrasound, avoiding positional bias, to predict fetal sex.

Results: The study delineated a clear distinction in AGD  measurements between male and female fetuses, with males presenting significantly longer AGD. Optimal AGD cut-offs were established  at 4.5 mm for weeks 11 to 12+6 days with an AUC of 0.967-0.988, indicating high diagnostic accuracy. At 13 weeks to 13 weeks  +6 days, a cut-off of 4.9 mm was identified, with an (Area under the Curve) AUC of 0.928. The predictive accuracy of fetal sex using  AGD was substantiated by a 100% confirmation rate of sex determination in the second trimester and post-delivery.

Conclusions: AGD  measurement in the first trimester presents a highly accurate, non-invasive method for early fetal sex determination.