[Twin gestation with regressive partial hydatidiform mole and coexisting live fetus].

The case of dichorionic twin pregnancy is described, with a fused placenta, one part of which is represented by a tissue of partial hydatidiform mole (PHM) with signs of regression, the second part is a placenta of a common structure with a normal development of the second twin. The delivery took place at the term of 38 weeks with a live healthy girl weighing 3250 g. A single placental disc consisted of two fused placentas with a clear boundary between them. The placenta of a live-born girl was mature, with focal chorangiosis, the second part of the disc was represented by the PHM tissue with avascular giant bizarre villi, some of them with central cisterns, with stromal fibrosis, low proliferative activity of the villous trophoblast and a significant narrowing of the intervillous space. A genetic study was carried out on the material of paraffin blocks from two parts of the placental disc containing the tissue of the villous chorion, and the blood of the parents. Comparative analysis of DNA isolated from the paraffin block of PHM with the DNA of the parents revealed the presence of diandric dispermic triploidy. No chromosomal pathology was found in the placenta of a living girl. For hydatidiform mole in the case of multiple pregnancy, an increase in the volume of the affected placenta is characteristic compared to the normal placenta of the twin. In our observation, the presence in the placenta with PHM signs characteristic of placentas with antenatal fetal death, stromal fibrosis of the villi and low proliferative activity of the trophoblast suggests a regression of PHM.