ULTRASONOGRAPHIC FETAL CARDIAC MEASUREMENT IN ISOIMMUNIZED PREGNANCIES

OBJECTIVE: To investigate the predictive value of the ultrasonographic ally measured fetal biventricular outer dimension (BVOD) in diastole i n detecting neonatal anemia in pregnancies complicated by isoimmunizat ion. STUDY DESIGN: The records of all patients evaluated for isoimmuni zation in pregnancy from January 1992 to December 1994 were reviewed r etrospectively. The fetal BVOD had been measured with real-time-direct ed M-mode fetal echocardiography. The BVOD measurement was plotted on a nomogram (with reference to biparietal diameter) and a percentile va lue determined graphically from the nomogram. Neonatal outcome was obt ained prospectively and by chart review. RESULTS: Sixty-three singleto n fetuses from the study period who met entry criteria were identified . Anti-D sensitization represented 66% of cases of isoimmunization. Tw enty (32%) fetuses required subsequent neonatal transfusion, and 43 (6 8%) did not. Seventeen fetuses (27%) had BVOD measurements greater tha n the 95th percentile, and 10 (59%) required subsequent transfusion. I nfants in this group also had significantly lower hematocrits at birth (37.7+/-13.0% vs. 46.6+/-9.0%) and prolonged neonatal intensive care unit stay (10.7+/-10.0 vs. 4.7+/-3.6 days), respectively, when compare d to patients with a BVOD measurement less than the 95th percentile. A BVOD 95th percentile threshold had a sensitivity, specificity and pos itive predictive value of 50%, 84% and 59%, respectively, in predictin g the need for neonatal transfusion. CONCLUSION: In patients with isoi mmunization, a BVOD measurement in the 95th percentile or greater was associated with a relatively high likelihood of neonatal anemia and tr ansfusion. Although the measurement is not sufficiently sensitive to b e used as a single parameter in predicting neonatal compromise in thes e patients, it can be a useful, noninvasive adjunct to the management of isoimmunized pregnancies.