Acute hemorrhage in monochorionic twins with ruptured velamentous vessels: anemic twin resuscitated by its co-twin through placental vascular anastomoses?

Monochorionic (MC) twin pregnancies are at increased risk of several complications including acute or chronic twin-twin transfusion syndrome (TTTS) and twin anemia-polycythemia sequence (TAPS). Both TTTS and TAPS result from inter-twin fetofetal transfusion through the placental vascular anastomoses. In addition, MC twin pregnancies are at increased risk of having a velamentous cord insertion, which has been linked with poor perinatal outcome due to risk of rupture of the velamentous vessels. In sporadic cases, these vascular connections may have a positive effect instead of a deleterious effect. We present a case of acute fetal distress in a MC twin pregnancy caused by acute hemorrhage following rupture of velamentous vessels. An emergency cesarean section delivery was performed at 29+2 weeks' gestation. One infant was severely anemic at birth and required immediate treatment with volume expansion and blood transfusion. Acute fetal blood loss through the ruptured vessels led to an acute fetofetal transfusion from the co-twin through the placental vascular anastomoses. Delayed intervention could have resulted in severe hypovolemic shock and acute anemia in both fetuses. Instead, in the current case, placental vascular anastomoses had a transient protective role and allowed transfusion of blood from one co-twin into the circulation of the anemic twin.