Prognostic value of the aortic isthmus Doppler assessment on late onset fetal growth restriction.

Background As conflicting results have been reported about the association of reversed flow on the aortic isthmus (AoI) and adverse perinatal results in fetal growth restriction (FGR), we aim to compare perinatal outcomes (including tolerance to labor induction) of late-onset FGR between those with anterograde and reversed AoI flow. Methods This was an observational retrospective cohort study on 148 singleton gestations diagnosed with late-onset FGR (diagnosis ≥32+0 weeks), with an estimated fetal weight (EFW) <10th centile and mild fetal Doppler alteration: umbilical artery (UA) pulsatility index (PI) >95th centile, middle cerebral artery (MCA)-PI <5th centile or cerebral-placental ratio <5th centile. Anterograde AoI flow was present in n=79 and reversed AoI flow in n=69. Delivery was recommended from 37 weeks in both groups. Perinatal results were compared between the groups. Results The global percentage of vaginal delivery of fetuses with anterograde and reversed blood flow was 55.7% vs. 66.7% (P=0.18) and the percentage of cesarean section (C-section) for non-reassuring fetal status was 12.7% vs. 15.9% (P=0.29), respectively. When evaluating those that underwent labor induction, the vaginal delivery rate was 67.9% vs. 77.2% (P=0.17), respectively. There were no significant differences regarding any other perinatal variables and there were no cases of severe morbidity or mortality. Conclusion We observed that the presence of reversed AoI flow does not worsen perinatal outcomes on fetuses with late-onset growth restriction with mild Doppler alterations. Attempt of labor induction is feasible in these fetuses regardless of the direction of AoI flow.