A 36-year-old pregnant woman with anti-HPA1a antibodies underwent six fetal platelet concentrate transfusions. During the second, at 28 weeks' gestation, fetal asystole occurred in association with a post-transfusion platelet count of 813 109/l. Asystole was reversed by an intracardiac partial exchange transfusion of normal saline for fetal blood, simultaneously reducing fetal plasma viscosity and enabling re-commencement of the fetal circulation.