Color Doppler imaging was used to investigate nine consecutive cases of placental tumors referred for evaluation to a tertiary referral unit. Gray-scale ultrasound findings were of a chorioangioma which was subsequently confirmed on pathologic examination. On color Doppler imaging (CDI), three tumors appeared avascular and the pregnancies were uncomplicated, two had only a few vessels in their periphery, and four contained numerous vessels. These vascular chorioangiomas were complicated by polyhydramnios and premature labor (n = 3), isolated polyhydramnios (n = 1), fetal growth restriction (n = 1) and generalized non-immune fetal hydrops (NIHF) (n = 1). The maximum diameter of the tumors ranged between 3 and 10 cm. There was no direct association between the size and location of the tumor and the development of complications. Successful amnioreduction was performed in the three cases of polyhydramnios and premature onset of labor. Vascular sclerosis was attempted unsuccessfully in the case complicated by severe NIHF. Our data indicate that the vascularization of the tumor is a pivotal determinant factor of pregnancy outcome. Where the tumor is avascular, no specific complications should be expected. Where the tumor is vascularized, and in particular if it contains numerous large vessels, serial ultrasound and Doppler examinations are warranted to detect polyhydramnios and early features of fetal congestive heart failure.