A triploid partial mole placenta from paternal isodisomy with a diploid fetus derived from one sperm and one oocyte may have caused angiogenic imbalance leading to preeclampsia-like symptoms at 19 weeks of gestation.

Partial hydatidiform mole with a normal fetus is extremely rare. A 30-year-old woman presented at 19 weeks gestation with clinical manifestations of severe preeclampsia. The fetus revealed a normal 46,XX karyotype and the placenta revealed triploid 69,XXX from paternal isodisomy. Microsatellite analysis revealed that the fetus and the triploid partial mole were derived from one sperm and one oocyte, followed by duplication of paternal chromosomes in only a trophectodermal cell. The maternal serum levels of angiogenic factors were extremely high compared with those reported in preeclampsia, suggesting an angiogenic imbalance may have caused preeclampsia-like symptoms before 20 weeks of gestation.