Figure 4b. Placental chorioangioma in a 35-year-old pregnant woman in the 24th week of gestation. (a) Transabdominal gray-scale US images show a well-defined hypoechoic mass containing multiple cystic spaces that protrudes from the fetal surface of the anterior placenta. (b) Color Doppler US image shows color signals in the cystic spaces. Spectral analysis shows arterial flow within the lesion. (c) Color Doppler US image of a different vessel with spectral analysis reveals venous flow within the lesion.