Structural Anomalies in Multifetal Gestations.

Multifetal gestations are at increased risk for structural anomalies relative to singletons. Determination of chorionicity is critical, as the risk is highest for monochorionic pregnancies. In a singleton gestation, counseling is structured around optimization of fetal outcomes and careful consideration of the patient's choices in management decisions. However, in multifetal gestations affected by a fetal anomaly, complex counseling with consideration for the pregnancy as a whole is necessary. We review the incidence of structural anomalies in twins and highlight unique considerations including selective termination for discordant anomalies. We emphasize the role of shared decision making between provider and patient.

Spontaneous septostomy in a monochorionic-diamniotic twin gestation.

Monochorionic twin gestations are associated with a greater incidence of neonatal morbidity and mortality when compared with their dichorionic counterparts. In turn, monochorionic-monoamniotic (MCMA) gestations carry greater risks compared with monochorionic-diamniotic (MCDA) gestations. While the true incidence of spontaneous septostomy of the dividing membranes (SSDM) in MCDA twins is unknown, SSDM has been demonstrated to be associated with increased morbidity and mortality, due to functional transition from a MCDA gestation to a MCMA gestation. We report a case of SSDM in a mid-trimester MCDA gestation, review the literature, and describe how to identify and manage this complication.