Background:Chorioangioma is the most common vascular placental tumor. Usualy its size is less than 4 cm and its prevalence is 1% (pathologicaly examined). Rarely, with prevalence of 1/3500, it is larger than 4 cm.A multiparus 27 years old G4D1L2 woman with gestational age of 33 weeks and with placenta tumor was refered to Al-Zahra hospital in December 2006. Due to abdominal distention, the patient underwent sonography and a large placenta chorioangioma was considered. Because of early onset of drops fetalis with spontaneous labor a newborn with 2250 gr weight and APGAR score of 10 was delivered; the weight of the placenta was 1100 gr with an 8×1×6cm tumor. The pathology result was chrioangioma.Key words:Pregnancy, placental tumor, hydrops fetalis, preterm labor