In this paper, we described a placenta with vesicular lesions in a 23-year-old woman (1-gravid) who visited our hospital at 13 weeks of gestation on prenatal routine examination. Ultrasound findings showed multiple vesicular lesions which gradually increased as the pregnancy advanced, and a live normal-appearing fetus which was confirmed of IUGR at 30 weeks of gestation in her uterus. Throughout gestation, the maternal serum β-human chorionic gonadotropin level keeps normal, but the serum alpha-fetoprotein was higher than average. The patient delivered an 1800-g female without obvious anomalies at 35 weeks 5 days of gestation due to premature rupture of membrane. The diagnosis of placental mesenchymal dysplasia was determined on the pathological examination and androgenetic/biparental mosaicism in the placenta was identified by immunohistochemical staining of p57kip2.