Doppler ultrasound velocimetry for timing the second intrauterine transfusion in fetuses with anemia from red cell alloimmunization

OBJECTIVE: Middle cerebral artery peak systolic velocity has been successfu lly used for timing the first cordocentesis in fetuses who are at risk for anemia because of maternal red cell alloimmunization. The effects on Dopple r velocimetry after the intrauterine transfusion of adult blood to these fe tuses are unknown. The objective of this study was to assess the applicabil ity of Doppler methods for the prediction of severe anemia in fetuses who h ad undergone 1 previous intrauterine transfusion. STUDY DESIGN: Doppler examination of middle cerebral artery peak systolic v elocity was performed before cordocentesis in 64 fetuses who had undergone 1 previous intrauterine transfusion. Timing of the second intrauterine tran sfusion was based on traditional criteria. Anemia was defined as mild (hemo globin value between 0.84 and 0.65 multiples of the median), moderate (hemo globin value <0.65-0.55 multiples of the median), and severe (hemoglobin va lue <0.55 multiples of the median). Receiver operator characteristic curves were created to select threshold values to identify the 3 degrees of anemi a with a sensitivity of 100%, RESULTS: Gestational age at the Doppler study ranged from 19 to 36 weeks, F orty-six fetuses (72%) were not or mildly anemic; 7 fetuses (11%) were mode rately anemic, and I I fetuses (17%) were severely anemic. Middle cerebral artery peak systolic velocity for the prediction of severe, moderate, and m ild anemia at a sensitivity of 100% showed false-positive rates of 6%, 37%, and 70%, respectively. CONCLUSION: In fetuses who have undergone 1 previous intrauterine transfusi on because of maternal red cell alloimmunization, timing the second intraut erine transfusion can be determined noninvasively by Doppler ultrasonograph y on the basis of an increase in the peak velocity of systolic blood flow i n the middle cerebral artery.