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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.