Fetal hypokinesia syndrome in the monochorionic pair of a triplet pregnancy secondary to severe disruptive cerebral injury.

We report a set of triplets, two of whom were monochorionic diamnionic and demonstrated cerebellar hypoplasia and progressive arthrogryposis on an antenatal sonogram. At delivery the infants exhibited a Pena-Shokier phenotype. At autopsy, the twins were concordant for severe disruptive lesions of the cerebrum. The mechanism resulting in the devastating symmetric lesions may have been a transient cerebral vascular compromise associated with placenta vascular anastomoses characteristic of monochorionic twinning. This report accentuates the vulnerability of the monochorionic twin for ischemic cerebral injury.