Background: Using anogenital distance to determine fetal sex is a new method. There is only one study in the literature. We predict that it will pass through the literature as a new method that can be used in determining fetal sex especially in first trimester. Introduction: Determination of fetal gender before birth has been a matter of curiosity for both the family and the clinician. In the presence of gender-linked genetic disease, it becomes an obligation instead of an interest. The aim of this study was to determine the fetal gender accurately at first trimester with anogenital distance (AGD) and to investigate the correlations of nuchal translucency (NT), fetal heart rate (FHR), and crown-rump length (CRL) with AGD. Materials and methods: In this prospective cross-sectional study, AGD measurement was performed in 111 patients with singleton pregnancy from 11 to 13 weeks and 6 days (CRL 45-84 mm). Measurements of AGD >= 4.8 mm were identified for males, and AGD Results: Genders were demonstrated accurately for males as 76.7% and for females as 97.1%. The mean value of AGD was 3.6 mm for females and 5.1 mm for males. There were no relations between fetal gender and FHR and also NT. Conclusions: Gender can be detected with great accuracy in gestations between 11 to 13 weeks and 6 days by using AGD. CRL and gestational week (GW) were determined as nonsignificant predictors of fetal gender by AGD measurement. In order to obtain more accurate results with AGD, consideration of further studies with larger series in different races is recommended.