15. A twin with a mole! A case report of an extremely rare condition of molar pregnancy with a coexisting fetus progressing to a viable infant

Abstract

<h3>Introduction</h3> Molar pregnancy with a coexisting twin fetus is an extreme rarity. The incidence of such an occurrence ranges from 1 in 10,000 to 100,000 pregnancies and this may increase with the greater use of assisted reproductive techniques. The management of these pregnancies is difficult due to complications such as fetal death, vaginal bleeding, pre-eclampsia and an increase risk for persistent trophoblastic disease. Delivery of a viable term normal infant from this combination is even rarer. <h3>Case report</h3> We report a case of molar pregnancy in a 36-year-old woman with a coexisting twin fetus which progressed to delivery of a viable healthy infant at term gestation. The submitted specimen was a twin placenta comprising two separate discs joined by a dividing membrane. One of the discs was pale yellow and small. Vesicles were not evident macroscopically. Microscopic examination showed a dichorionic diamniotic twin gestation. The placenta of the viable term gestation showed no significant abnormality while the separate yellow disc showed changes of hydatidiform mole with extensive infarct-like necrosis. <h3>Discussion</h3> Molar pregnancy with a coexisting twin fetus progressing to a healthy infant is an extremely rare entity. The management guidelines for decision making are limited as there are only a few published reports in the literature. We present this case report to highlight the existence of this extremely rare entity. In addition, it demonstrates that, despite the presence of a coexisting molar gestation, the non-molar gestation may progress to delivery of a normal healthy term infant.