Villitis of unknown etiology, chronic deciduitis, chronic chorioamnionitis and chronic histiocytic intervillositis in monozygotic and dizygotic twin pregnancies. A retrospective analysis of 16 cases.

INTRODUCTION: Villitis of unknown etiology (VUE), chronic chorioamnionitis (CC), chronic deciduitis (CD) and chronic histiocytic intervillositis (CHI) are most likely the result of a pathologic immune reaction caused by maternal anti-fetal rejection. We analyzed placentas of twin pregnancies with manifestation of these lesions in monozygotic and dizygotic instances.

METHODS: Twin pregnancies from our archive with at least one chronic inflammatory lesion were selected for further analysis and assessed concerning zygosity (gender, chorionicity, short tandem repeat (STR)-analysis).

RESULTS: The cohort comprised sixteen twin placentas, monozygotic in five cases and dizygotic in 11 cases, respectively. VUE (n = 4), CC (n = 1) and CHI (n = 3) manifested concordantly in both placentas of the monozygotic pregnancies and affected discordantly one of the twin placentas in the dizygotic instances. CD (n = 10) manifested concordantly in two and discordantly in one of the monozygotic placentas, and concordantly in three and discordantly in four of the dizygotic instances. Intrauterine fetal demise (n = 3), preterm birth (n = 9) and low birth weight (n = 2) were recognized. Discordant fetal growth in live born children was recognized in two dizygotic cases with discordant manifestation of VUE and CHI.

DISCUSSION: The concordant manifestation of VUE, CC and CHI in monozygotic and the discordant pattern of inflammation in dizygotic pregnancies points to pathologic immune mechanisms against genetically determined fetal antigens being essential for the development of these entities. The heterogenous manifestation of CD could be a hint for diverse fetal or maternal etiologic factors that may contribute to this lesion.