Monochorionicity: Unveiling the pandora box

Abstract

This article reviews the phenomenon of monozygosity by conducting an exhaustive literature review of this special type of twin pregnancies. An epidemiological update is presented showing the substantial contribution to perinatal morbidity and mortality as well as the increasing incidence associated with assisted reproductive techniques. Molecular mechanisms of zygosity and chorionicity are explored and the processes that lead to differences in monozygotic twin pairs are identified. A diagnostic sequence is proposed considering the modifications relative to singleton pregnancies as well as the pathology unique to this pregnancy type.