Symmetric and ventrally conjoined twins: prenatal evaluation by ultrasound and magnetic resonance imaging and postnatal outcomes.

Objective: To review the perinatal and long-term outcomes of symmetric and ventrally conjoined twins evaluated prenatally by ultrasound and fetal magnetic resonance imaging (MRI).

Methods: From March 2010 to January 2019, cases of symmetric and ventrally conjoined twins, who were prenatally diagnosed and referred to the Clínica Diagnóstico por Imagem (CDPI), Rio de Janeiro, Brazil, for prenatal evaluation by ultrasound and MRI were selected. The postnatal information was collected from hospitals where the twins were born and/or treated and from parents' verbal and written information.

Results: Four cases of symmetrical and ventrally conjoined twins were selected. Of these, two were omphalopagi and two thoracopagi. One pair of thoracomphalopagus died early and the other died 6 days after birth. The outcome of the two omphalopagus pairs were separation in emergency surgeries after birth, with neonatal demise of one of the twins due to congenital malformations. In cases of omphalopagi, fetal MRI presented important information of the twins' anatomy before emergency separation of both pairs.

Conclusion: Despite the apparently similar conditions of twins with ventral fusion, ventrally attached twins have very different outcomes, most adverse for thoracomphalopagus and related to the singular anatomy of the pair, associated malformations and the extension of the adhesion, requiring individual evaluation of the cases. Fetal MRI is as an important tool for the postnatal surgery management of twin neonates, providing crucial information in cases where urgent separation is required.