Intrauterine sonographic visualization of embryonic genital tubercle

To visualize embryonic genital tubercle using intrauterine sonography with a 20-MHz flexible catheter-based high-resolution real-time miniature transducer in early first-trimester pregnancy.

Randomized prospective study.

A total of 39 women about to undergo therapeutic abortion from 7 to 10 weeks' gestational age were studied with specially developed catheter-based high-resolution real-time miniature (2.4 mm in outer diameter) ultrasound transducer (20 MHz). Before the intrauterine sonographic procedure was performed, transvaginal sonographic assessment of the embryo was conducted. The percentage of embryonic genital tubercle (or phallus) visualized at each gestational age using intrauterine and transvaginal sonography is presented.

The genital tubercle could not be identified at 7 weeks of gestation with intrauterine sonography. The genital tubercle was visualized in 30% of embryos at 8 weeks' gestation, and in 100% of embryos at 9 and 10 weeks. The genital tubercle was situated somewhat cranially to the sacral prominence at this gestational age. The genital tubercle could not be depicted with transvaginal sonography between 7 and 10 weeks of gestation.

Intrauterine sonography provides a novel means for visualization of genital tubercle of the embryo. These results suggest that intrauterine sonography can become an important modality in future embryological research and in detection of embryonic developmental disorders in the early first-trimester pregnancy.