Diagnosis and outcome of complete hydatidiform mole coexisting with a live twin fetus

Objective: The aim of this study was to highlight the outcome of complete hydatidiform mole (CHM) coexisting with a live co-twin. Methods: We investigated four cases of such pregnancy by ultrasound, pathological, cytogenetic, and molecular techniques. Information on clinical follow-up and outcome was also available. Results: All four pregnancies were spontaneous: two ended with the delivery of a live-born baby, while the other two were terminated because of signs of serious maternal pathology or intrauterine fetal death. The criteria for carrying on with the pregnancy are reviewed. The immediate outcome depends on the maternal criteria of serious pathology and on the likelihood of intrauterine fetal death. The risk of persistent trophoblastic disease (PTD) is the same as in the case of a singleton complete mole and also seems to be correlated with the zygosity mechanism identified by molecular analysis. Conclusion: Hydatiform mole with a live co-twin fetus is a rare obstetric occurrence. In the case of a normal fetal karyotype, it is justifiable to await developments in the absence of maternal complications. However, treatment criteria still need improvement and diligent maternal follow-up is always warranted in the postpartum period.