CAN A SINGLE MEASUREMENT OF AMNIOTIC-FLUID DELTA-OPTICAL-DENSITY BE SAFELY USED IN THE CLINICAL MANAGEMENT OF RHESUS-ALLOIMMUNIZED PREGNANCIES BEFORE 27 WEEKS GESTATION

Background To assess the efficacy of a single measurement of amniotic fluid optical density deviation at 450 nanometers in predicting fetal anemia in Rhesus-alloimmunization before 27 weeks gestation. Methods. In this cross-sectional study, fetal blood and amniotic fluid samples from 43 Rhesus-alloimmunized pregnancies at 18 to 26 weeks gestation w ere obtained under ultrasound guidance. Amniotic fluid samples were sc anned by spectrophotometry for optic density at various wavelengths. D eviation at 450 nanometers was calculated between 550 and 365 nanomete rs. The fetuses were divided into three groups based on their hematocr it levels and the predictive efficacy of optic density zones for anemi a was evaluated. Results. A high number of false positive and false ne gative results were observed when the delta-amniotic fluid optical den sity of fetuses at risk for anemia was plotted to the zones recently p roposed to manage Rhesus-alloimmunized pregnancies. Conclusions. These data confirm previous results that the diagnosis of fetal anemia in R hesus-alloimmunized pregnancies before 27 weeks' gestation cannot be a ccurately made by a single measurement of amniotic fluid optical densi ty at 450 nanometers.