Uterine venous blood flow in normal and complicated pregnancies: a methodological study.

ABSTRACT

OBJECTIVE: To investigate the possibility of recording Doppler flow signals from the maternal uterine veins (UtVs) during pregnancy and to assess the relationship between UtV signals and other Doppler parameters as well as pregnancy outcomes. METHODS: Transabdominal Doppler ultrasound examination of the UtVs on both sides of the uterus was performed in 40 normal and 44 high-risk singleton pregnancies at 23-39 weeks' gestation. The UtV was identified using color Doppler imaging and the flow velocity signals of the UtV and uterine artery (UtA) were recorded. Morphological examination of the placenta was carried out in 45 of the pregnancies (14 uncomplicated and 31 high-risk pregnancies). RESULTS: Flow-velocity signals of the UtVs were recorded from at least one side of the uterus in all patients (success rate of 81 and 89% for the right and left UtV, respectively). Three types of flow-velocity pattern were identified continuous non-pulsatile flow (Type I, n = 70), pulsatile flow with a notch touching the zero line (Type II, n = 6) and pulsatile flow with absent flow signals for part of the heart cycle (Type III, n = 8). The UtA pulsatility index was significantly higher in women with UtV Types II and III than in those with UtV Type I (P = 0.039). Similarly, UtV Types II and III were more often found in pregnancies with bilateral UtA notching (P = 0.013) and with UtA score 3-4 (P = 0.024) than in those with normal UtA. No statistically significant association was found between the UtV flow pattern and abnormal histopathological findings in the placenta, or between the UtV and umbilical artery findings. CONCLUSION: It is possible to record Doppler signals from the UtVs in the late second and third trimesters of pregnancy. Pulsatile flow-velocity patterns of the UtVs are associated with abnormal UtA Doppler findings.