Fetal arterial and venous Doppler parameters in the interpretation of oligohydramnios in postterm pregnancies

Objective The objective of the current study was to evaluate fetal arterial and venous Doppler parameters in postterm pregnancies with oligohydramnios and those with normal amniotic;fluid. Study Design A cross-sectional study was performed in 38 pregnancies beyond 41 weeks' gestation. Pulsed Doppler imaging was used to determine the puls atility index (PI) for the fetal middle cerebral artery (MCA), renal artery , umbilical artery, inferior vena cava (IVC) and ductus venosus. The amniot ic fluid index (AFI) was used for semiquantitive assessment of amniotic flu id volume. Oligohydramnios was defined as an AFI < 5 cm. Results Oligohydramnios was detected in 10 cases, and a normal AFI was pres ent in 28 cases. In the presence of oligohydramnios the PI of the MCA was d ecreased, while the renal artery PI and the MCA PI/UA PI ratio were found t o be elevated. In cases of oligohydramnios the PI in the IVC was increased but was unchanged in the ductus venosus. Conclusion Oligohydramnios in post-term pregnancies is associated with arte rial redistribution of fetal blood flow typifying the brain sparing effect and with decreased resistance in the MCA and increased resistance in the fe tal IVC.