Massive subchorial thrombohaematoma (Breus' mole).

Ten placentae with massive subchorionic thrombohaematomas are reported. This lesion, which is composed of maternal clotted blood, separates the chorionic plate of the placenta from the villous chorion and is traversed by the main cotyledonary branches of the fetal circulation. In some instances it dissects into the layers of the chorionic plate. In anatomical terms it is identical to the lesion which has been described in early pregnancy under the title of Breus' mole. Previous reports suggested that the lesion was confined to early pregnancies and was a consequence of fetal death. In our series all ten placentae were from pregnancies of at least 25 weeks' maturity and six were more than 30 weeks. Seven infants were liveborn and three survived the neonatal period. Differential diagnosis is discussed along with aetiology, which is still obscure although earlier theories implicating fetal death may be discounted.