Severe fetal anemia after umbilical cord occlusion leading to severe neurological injury in monochorionic twins.

We describe two cases of monochorionic twins with severe anemia in the surviving twin after cord occlusion. The first one was a case of discordant malformation (anencephalia) and the second one was a case of early severe selective intrauterine growth restriction type II in a dichorionic triamniotic triplet pregnancy. In both cases, the cord of the occluded fetus had a marginal insertion. Both of them presented hydrops 2 d after the occlusion, having measurements of the peak systolic velocity (PSV) of the middle cerebral artery (MCA) above 1.5 multiples of the median (MoM). In the first one intrauterine transfusion was performed with pretransfusion measurement of fetal hemoglobin of 3.3 g/dL. An extensive area of destruction of brain tissue at the right parietal-temporal-occipital level was diagnosed at 300 weeks. In the second one, expectant management was decided and a grade 3 intraventricular hemorrhage associated with moderate ventriculomegaly was detected at 22 weeks' gestation. We hypothesize that the surviving fetus after the occlusion can become bloodless and hypovolemic when its blood is poured into the placental and umbilical circulation of the occluded twin through the vascular anastomoses between them. It should not be assumed that cord occlusion removes the risk of transfusional brain injury in surviving-cotwins.