Background: Pregnancies that extend beyond due date (post-term) are associated with an increased risk of complications for both the mother and fetus, including morbidity and mortality.  Doppler ultrasound offers a non-invasive way to assess blood flow patterns in the fetal renal artery, but the current evidence regarding the link between altered renal flow and oligohydramnios (low amniotic fluid volume) remains inconclusive.
Objectives: To assess the correlation between fetal renal artery Doppler measurements and amniotic fluid volume indices.
Patients and methods: In a study of 68 post-term pregnant women, two groups were formed. The first group had oligohydramnios (AFI < 5 cm), while the second group had normal amniotic fluid capacity (AFI > 5-25 cm). Researchers conducted a thorough history, sonographic evaluation, clinical examination, and standard laboratory tests. Doppler examination assessed fetal renal artery characteristics, including blood flow (FRABF), resistance index (RI), pulsatility index (PI), acceleration time (AT), and systolic/diastolic ratio (S/D).
Results: A significant positive correlation between AFI and FRABF were identified in our investigation. On the other hand, AFI exhibited substantial negative correlations with the doppler of renal artery indices: RI, PI, PS, and AT (correlation coefficients r=-0.549, r=-0.330, r=-0.258, and r=-0.478, respectively; all p-values<0.05). Furthermore, the Doppler indices of the study and control groups demonstrated significant differences statistically (all p-values<0.05).
Conclusions: Doppler ultrasonography reveals a link between oligohydramnios and renal artery flow waveforms. Changes in RI, PI, AT, and FRABF values can serve as rapid delivery indicators in post-term pregnancies with reduced amniotic fluid volume.