RESUMEN
Placental mesenchymal dysplasia is a rare condition of pregnancy that present as macroscopic feature of molar change in the placenta and normal karyotype fetus, and has been reported at birth in 15 cases of Beckwith-Wiedmann syndrome and 25 cases of normal fetus in literatures. It may mimic the partial hydatidiform mole, but the mesenchymal dysplasia is different that it may be compatible with a normal fetus. A nulliparous woman was suspected to be a partial mole with a coexistent live fetus in gestational age of 14 weeks because of the partially cystic placenta on ultrasonography examination. She delivered a healthy female vaginally at 36+6 weeks of gestation and the histological examination of placenta established the diagnosis of mesenchymal stem villous dysplasia. We report here an unusual pregnancy.