Doppler assessment of fetal aortic isthmus flow in twin

Abstract

Objective The purpose of this study was to investigate the aortic isthmus (AoI) flow difference between larger fetus and smallerfetus of twin; and to evaluate the predictive value of early diagnosis of hemodynamic change in twin growth. Methods This prospective study on 49 pairs of twin fetuses was performed to obtain AoI blood flow data. Cases with structuralor chromosomal abnormalities and co-twin death were excluded. The interval from examination to delivery was within4 weeks and 3 cases over 4 weeks interval were re-examined. Assessment of fetal AoI Doppler parameters were peaksystolic velocity (PSV), end-diastolic velocity, times-averaged maximum velocities, pulsatility index (PI), and resistanceindex (RI). According to the direction of the diastolic flow in the AoI, antegrade and retrograde flow were made and wasused to analyze the perinatal outcomes of each fetus. The predictive value of AoI Doppler parameters in predicting fetalgrowth was obtained by using ANOVA and logistic regression analysis of quantitative variables in each fetus of twins. Results There were significant differences in the gestational weeks at delivery, birth weight and the incidence of growthdiscordance over 20% or more between monochorionic twin and dichorionic twin. The AoI PI and RI were significantlyhigher in smaller fetus than in larger regardless of chorionicity. Retrograde flow was noted in 8 of 98 cases (8.2%) andthe only one case was of the larger fetus and the others were smaller fetuses of twin. Significant correlations werefound between the AoI PI and birthweight (P=0.018) and between the PSV and growth discordance (P=0.032). Inmonochorionic twin, linear correlation was shown between the AoI PI and birthweight (P=0.004) and between AoI PIand growth discordance (P=0.031). Also, the meaningful correlation between the PSV and birthweight (P=0.036) wasfound by using logistic regression analyses. ConclusionOn the basis of our observation, AoI PI has revealed their hemodynamic status and this result may improve theunderstanding of growth patterns in twins.