Intrauterine transfusion in monochorionic twins with parvovirus B19 infection: Evidence of intertwin blood exchange.

BACKGROUND: Parvovirus B19 infection can cause severe fetal anemia. Management in monochorionic twin pregnancies is challenging due to placental vascular connections. CASE: We report a case of severe fetal anemia in both fetuses of a monochorionic diamniotic twin pregnancy following maternal parvovirus B19 infection. Elevated middle cerebral artery peak systolic velocity (MCA-PSV) was first detected at 16 weeks in twin A and reached 2.32 multiples of the median (MoM) in twin A and 2.30 MoM in twin B at 21+6 weeks. These findings were associated with polyhydramnios in both fetuses and ascites in twin B. Intrauterine transfusion was performed at 22+1 weeks, revealing hemoglobin levels of 3 g/dL in both fetuses. Transfusion of twin B resulted in an unexpected spontaneous increase in hemoglobin in twin A, suggesting intertwin blood transfer. RESULTS: Following minimal additional transfusion in twin A, MCA-PSV normalized in both fetuses. The pregnancy was subsequently complicated by preeclampsia without severe features, and vaginal delivery occurred at 36+3 weeks. Both neonates had normal and identical hemoglobin levels at birth. Placental examination after delivery, with dye injection, demonstrated a single large arterio-arterial anastomosis that had not been visualized prenatally. CONCLUSION: Transfusion of one twin was followed by an immediate rise in hemoglobin in the co-twin, indicating major intertwin blood exchange through a large arterio-arterial anastomosis. Because such exchange cannot be predicted prenatally, both fetuses require individual assessment before and after transfusion.