Abnormal fetal genitalia: two- and three-dimensional ultrasound assessment

To evaluate the incidence of abnormal external genitalia of the fetus and discuss the accuracy of its prenatal diagnosis using two-(2D)/three-(3D) dimensional ultrasound in second- and third-trimester fetal screenings.

During the 24 months, second- and third-trimester fetal screenings were performed at 18-21+6 and 28-31+6 weeks of gestation, respectively, in 1,623 pregnant women. Fetal external genitalia were assessed using 2D/3D ultrasound. After birth, cross-examination was performed by pediatric experts to check the external genitalia.

Twelve cases of abnormal genitalia (hypospadias: 3; hypospadias with penoscrotal web: 1; micropenis: 3; buried penis: 2; clitoromegaly: 2; genital tumor: 1) were suspected prenatally (0.74 %). In 9 fetuses with suspected abnormal male genitalia, the penile length was below the lower 90th confidence interval. In 2 fetuses with suspected clitoromegaly, the clitoral length was above 6.5 mm. In the 9 fetuses with suspected abnormal male external genitalia, only 6 (hypospadias: 2; penoscrotal web with mild chordee: 1; micropenis: 1; buried penis: 2) were diagnosed postnatally (66.7 %), whereas 3 were diagnosed as normal. Mixed gonadal dysgenesis (45X/46XY) was diagnosed in 1 neonate with hypospadias. One neonate with a micropenis had a right aortic arch and persistent foramen ovale. In 3 fetuses with suspected abnormal female external genitalia, prenatal findings were considered transient, and normality was confirmed after birth.

Prenatal diagnosis of abnormal external genitalia may still be difficult even with 3D ultrasound. Postnatal cross-examination by pediatric experts should be mandatory when abnormal external genitalia are suspected prenatally.