Stroke in pediatric age is a rare event with a multifactorial genesis which could involve genetic factors as methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphism. At the same time, twin gestation with co-twin demise is an important potential risk factor for premature brain damage.We describe two children presenting with presumed cerebral stroke born from two MC twin pregnancies in which the other co-twin had died in utero associated to maternal and fetal homozygosity for MTHFR C677T and MTHFR A1298C, respectively. Brain damage was diagnosed immediately before the delivery.Our observations underline the necessity to make a thrombophilia workup in women before or during pregnancy and, above all, in twin pregnancy. Data of literature are not clear about what kind of genetic polymorphism is prominent in the genesis of cerebral stroke (factor V leiden, MTHFR, activated protein C resistance, factor II G20210A). A multifactorial genesis for severe fetal and perinatal cerebral vascular alterations has been supposed; for this reason an early folate supplementation both to mother and infant could reduce the risk of brain damage due to fetal/perinatal stroke and eventual recurrence of thrombotic events.