Clinical Investigation

First Trimester Fetal Gender Assignment by Ultrasound

  • Sabahattin Altunyurt
  • Halil Gürsoy Pala
  • Özge Piri Mantar

Turk J Obstet Gynecol 2010;7(1):23-28


To investigate the efficiency of genital tubercule angle on detecting fetal gender in first trimester by ultrasonography.


Fetal sex assignment by ultrasound was carried out in 172 pregnancies at 11-13+6 weeks between 2007 June and 2007 December. Gestational age was determined by the measurement of crown-rump length (CRL). The ultrasound predictions were compared with actual sex at birth. Mid-sagittal planes of a section of the fetal genital tubercle were performed to identify the gender.


155 of 172 patients’ data were achieved. The overall success rate was 92.3 % in sonographic assignment of fetal sex. The correct assignment rate in female fetuses was significantly higher than males (95.9 % - 88.8 %) [p=0,001]. The correct identification of fetal sex improved with advancing gestational age from 89.3 % between 11-11+6 weeks, 92.5 % between 12-12+6 weeks and 93.4 % between 13-13+6 weeks (p=0,96).


The fetal sex assignment by ultrasonography between 11-13+6 weeks had high success rate. The sensitivity of fetal sex assignment was not affected with fetus position and gestational age.

Keywords: Ultrasonography, Pregnancy trimester, first, Gender identity