Reference ranges for doppler parameters of fetal aortic isthmus during the second half of pregnancy

Abstract

Doppler study of umbilical artery, middle cerebral artery, uterine arteries and ductus venosus which is done routinely has its own limitations. The emergence of aortic isthmus index as an ideal parameter that provide an early detection of hemodynamic disturbance inside the fetus in the late pregnancy due to its position as a shunt between right and left ventricle, has inspired the study. Objectives of this study is determine the gestational age specific doppler indeces in fetal aortic isthmus flow in third trimester gestation and to compare the changes with varying time period of third trimester of gestation.

Materials and Methods: A total of 325 normal pregnancies with gestational age of 28 to 40 weeks by first trimester ultrasound were included in the study. Study was done during May, 2020 to July, 2021 in Alzahra hospital, Tabriz, Iran. Aortic isthmus doppler flow indices namely PSV, EDV, RI, PI, IFI, S/D and TAMAX were automatically calculated in GE voluson E8 machine with 2-5 MHz probe and compared by their Ultrasound derived gestational ages. The correlations of doppler indices with gestational age was determined by regression equation. Results: It was observed that PSV, EDV, PI and TAMAX increases with gestational age with correlation coefficient R^2=0.15, 0.044, 0.098 and 0.079 respectively and p value <05/0. RI, IFI and S/D didn’t show any correlation with gestational age.