Fetal MRI findings in conjoined twin pregnancies

Conjoined twins are a rare and complex anomaly of monozygotic twin gestations, in which there is joining of the bodies of two individuals. Prenatal imaging, including fetal MRI, plays a crucial role in prognostication and planning for these twins' families and multi-disciplinary medical teams. The ability of fetal MRI to provide large field-of-view imaging is well-suited to delineate the complicated shared and individual anatomy of these twins. In this review, we describe an approach to the fetal MRI of conjoined twins and its limitations, illustrate the fetal MRI findings of the conjoined twin morphological variants, and discuss common superimposed anomalies. The anatomic features most predictive of these twins' chances for survival and separation are also summarized.