Clinical utility of aortic isthmus Doppler in the prediction of perinatal outcomes

BACKGROUND: Doppler studies of uteroplacental–fetal circulation have been proven useful in diagnosing fetal growth restriction, appropriately timing delivery, and improving perinatal morbidity and mortality. There has been an extensive search for the ideal means to identify fetuses between the compensatory and acidemic phase (ie, the “preacidemic phase”), and the aortic isthmus Doppler seems to show promise. OBJECTIVE: This study aimed to investigate: (1) the prevalence of abnormal aortic isthmus Dopplers in a cohort of small-for-gestational-age fetuses and their correlation with other conventional Doppler abnormalities, and (2) the predictive ability of abnormal aortic isthmus Dopplers with regard to short-term adverse neonatal outcomes. STUDY DESIGN: Fetuses diagnosed as small-for-gestational-age at ≥24 weeks’ gestation were included. Management was as per the standard protocol. Aortic isthmus Doppler was performed within a week of delivery with other conventional Dopplers. The adverse perinatal outcomes studied were: requirement of neonatal resuscitation at birth, Apgar score at 5 minutes <7, cord blood pH <7, presence of bronchopulmonary dysplasia, hypoxic-ischemic encephalopathy, grade III/IV intraventricular hemorrhage, necrotizing enterocolitis, sepsis, neonatal intensive care unit stay longer than 14 days, and stillbirth or neonatal death. RESULTS: Among 121 small-for-gestational-age fetuses, 67 showed Doppler abnormalities in ≥1 vessels. The prevalence of abnormal aortic isthmus Doppler was 14.87%. Analysis was between group 1 with 103 normal aortic isthmus and group 2 with 18 abnormal aortic isthmus fetuses; 41 cases had some form of adverse perinatal outcome, the frequency of which was comparable between the groups. Abnormal aortic isthmus Doppler had a significant correlation with low cerebroplacental ratio, absent or reversed end-diastolic flow in the umbilical artery, and high pulsatility index in the ductus venosus. The positive likelihood ratio for predicting composite adverse perinatal outcome was 10.2 for absent or reversed end-diastolic flow in the umbilical artery, 9.6 for low cerebroplacental ratio, 2.28 for absent or retrograde flow in the aortic isthmus, and 2 for abnormal ductus venosus. CONCLUSION: Predelivery abnormal aortic isthmus Dopplers performed worse than other conventional Dopplers in predicting abnormal perinatal outcomes.