Rare spontaneous monochorionic dizygotic twins: a case report and a systematic review

Abstract

Background Monochorionic dizygotic twins are a rare condition, mostly related to assisted reproductive technology. This type of twinning is burdened by the same risk of pregnancy complications found in monochorionic monozygotic pregnancies. Case presentation We report a case of spontaneous monochorionic dizygotic twins sharing situs inversus abdominalis and isolated levocardia, with only one twin affected by biliary atresia with splenic malformation syndrome. We also conducted a literature review of the 14 available documented monochorionic dizygotic twin gestations spontaneously conceived. Conclusions It is still unclear how this unusual type of twinning can occur in spontaneous conception. The evidence so far suggest the importance to timely diagnose the chorionicity, in order to adequately manage the typical complications associated with monochorionicity.

Phenotypically Discordant Anomalies in Conjoined Twins: Quirks of Nature Governed by Molecular Pathways?

“…Moreover, it is oftentimes brought up as a fact that DZ twins are dichorionic and that monochorionicity is exclusively seen within MZ twins. Nonetheless, observations of monochorionic DZ twins [69,70] with discordant sex [71][72][73] contradict the accepted principle that monochorionicity is proof of monozygosity and opposes the current model of MZ and DZ twinning. Another issue when thinking about zygosity and chorionicity rises from the often absent information on the determination of zygosity in same-sex twins, as some identical-sex MZ twins could actually be DZ twins, again challenging the current model of twinning [74].…”

Prenatal Diagnosis of Canine and Feline Twins Using Ultrasound: A Retrospective Study

“…In monochorionic twins and, at least, in dogs, dizygosis seems more frequent than monozygosis. In humans, most monochorionic twins are monozygotic; dizygosis has been documented and considered an extremely rare condition [34]. The occurrence of monozygotic dichorionic diamniotic twins is not excluded, although it has never been documented in these species.…”

“…A general rule exists in the field of obstetrics according to which monochorionic twins are almost exclusively monozygotic [33]. However, monochorionic dizygotic twins have been reported in humans after assisted reproductive technologies [34] and in dogs [20]. On the other hand, dichorionic dizygotic twins are the norm, and dichorionic monozygotic twins are extremely rare [35].…”