Main Findings-
There is a diversity and lack of uniform model which would reflect hemodynamic changes in pregnancy with IUGR. The surveillance of these IUGR cases and taking a clear cut decision whether to deliver these fetuses or not and if when, thus weighing the risk of intrauterine death by prolonging the gestation versus delivering the fetus prematurely is the major concern. Our data call into question whether can be use retrograde flow in aortic isthmus as a trigger to deliver these growth restricted fetuses.
This study supports the association of retrograde flow in the aortic isthmus with the adverse perinatal outcome as suggested by[13] M.Del Rio et al and Hidar et al[14]. In our study, Retrograde AoI group had higher rates of adverse perinatal outcome (92.3% vs. 72%). Abnormal AoI had sensitivity of 63.1%, a high specificity (87.5%) and a PPV (92.3%) and likelihood ratio (5) for prediction of adverse perinatal outcome. Overall perinatal mortality (intrauterine death and neonatal death) was higher in retrograde group 3/13(23%).There was no perinatal mortality in antegrade flow in AoI group. Thus suggesting a potential role for Doppler imaging of the AoI in the clinical surveillance of severe IUGR fetuses .
In our study, there was a highly significant association of retrograde diastolic aortic isthmus flow with abnormal umbilical artery (92.3% vs. 36%) (p =0.013) similar to study by Del rio etal[13] . Thus suggesting that retrograde diastolic flow in the AOI represents a group with more severe and earlier onset of placental insufficiency.
In a study by del rio et al[13] and Makikallio K et al[15 ] , MCA vasodilatation did not differ between the antegrade and retrograde groups .However in our study ,MCA vasodilatation differed in the antegrade and retrograde groups (48% vs. 92.3%) respectively .
Similar to Del rio et al[13], our study shown a strong association between the presence of abnormal DV flow and retrograde flow in the AoI. (38% vs. 8%)( P= 0.034). 5/7(71.4%) of cases with abnormal DV flow had reverse diastolic flow in the AOI. This suggests well corelation of these parameters with the progressive deterioration of cardiac function occurring in IUGR. All these findings suggested significant corelation of retrograde flow in aortic isthmus with abnormal flow in UA,MCA and DV.
Del rio et al[13] proposed that AoI PI and DV-PI independently predict adverse outcome. And in preterm growth restricted fetuses, AoI blood flow becomes abnormal on average 1 week before DV blood flow does. In our study ,retrograde flow in AoI was seen on an average 2 days before delivery and abnormal DV PI was seen 1 day before delivery .
We have also analyzed, the fetuses with AEDF or REDF in UA with retrograde AoI by sub grouping as, those having normal DV and those with Abnormal DV .There were 2 perinatal deaths from the group with normal DV while 1 NND from abnormal DV group . So , even with normal DV Doppler flow the perinatal mortality (40%)was found in AEDF/REDF with retrograde AOI group .Thus even though the DV flow is normal adverse outcome might be suspected in fetuses with AEDF/REDF in UA and retrograde flow in AoI. Thus providing a better window for delivering the IUGR fetuses before failure of fetal compensatory mechanisms to hypoxia.
Results
Our study confirms previous observations that retrograde blood flow in the AoI is associated with adverse perinatal outcome, particularly intrauterine demise ,neonatal death ,RDS. Retrograde flow in AoI correlates significantly with abnormal flow in Umbilical artery, Middle cerebral artery and Ductus venosus.
Abnormal aortic isthmus flow is generally seen prior to abnormal changes Ductus venosus Doppler .
Clinical Implications –
Even though the DV flow is normal adverse outcome might be suspected in fetuses with AEDF/REDF in UA and retrograde flow in AoI. Thus providing a better window for delivering the IUGR fetuses before failure of fetal compensatory mechanisms to hypoxia.
Thus retrograde flow in AoI might be considered as an additional trigger for delivering IUGR fetuses between 30-34 weeks with AREDF in UA.
Also , AoI Doppler might be considered as an additional clinical parameter in the routine assessment of hemodynamically compromised growth-restricted fetuses.