The Morphology of the Genital Tubercle: A Macroscopic Assessment and Ultrasound Approach on Early Fetal Sex Determination.

Background/

Objectives

The genital tubercle develops in the fourth week from mesenchymal cells in the lateral edges of the embryo. In females the genital tubercle develops into the clitoris while in males it participates in forming the penis. The aim of this study was to perform a macroscopic as well as an ultrasonographic assessment of the genital tubercle and its gender-dependent derivates, presenting a parallel comparative evaluation between the two.

Methods

We performed a morphological assessment of the genital tubercle through micro-dissection of 141 embryos and fetuses with gestational ages between 5 and 14 weeks, in the Department of Anatomy of "Carol Davila" University of Medicine and Pharmacy. An ultrasound imaging study of the genital tubercle using 3-dimensional ultrasonography (3DUS) was also performed in the Department of Obstetrics and Gynecology of University Emergency Hospital of Bucharest. The morphology of the genital tubercle was analyzed by ultrasound scanning of 119 embryos and fetuses with gestational ages between 5 and 14 weeks. The age of all the embryos was determined by measuring the crown-rump length.

Results

The dimensions and especially the direction of the genital tubercle were evaluated and compared in order to establish whether sex determination is possible as early as 7-8 weeks of gestation. The genital tubercle orientates cranially in males and caudally in females as early as 6 weeks of gestation, during the bi-potential phase.

Conclusions

The orientation of the genital tubercle plays an essential role in establishing the sex of the fetus, regardless of its size.