Background: Fetomaternal hemorrhage is a rare cause of fetal anemia and hydrops fetalis. Early and severe fetomaternal hemorrhage may benefit from in utero transfusion(s); however, hemorrhage rate is unpredictable, and reliable criteria are needed to identify recurrent anemia.
Case: Fetal hydrops due to massive fetomaternal hemorrhage was diagnosed at 29 weeks. After the first in utero transfusion, daily monitoring of middle cerebral artery peak systolic velocity suggested recurrent fetal anemia, requiring two additional in utero transfusions at 1-week intervals. One day after the third in utero transfusion, a sudden increase in fetomaternal hemorrhage rate was suspected on a rapid elevation of middle cerebral artery peak systolic velocity, leading to immediate delivery at 32 weeks.
Conclusion: Middle cerebral artery peak systolic velocity is a relevant, noninvasive tool for the timing of repeated in utero transfusions and of fetal delivery in case of chronic fetomaternal hemorrhage.