Correlation of Ultrasound Umbilical Venous Blood Flow in Normal Pregnancy with Gestational Age and Foetal Weight

Background: Umbilical venous (UV) blood flow is a direct and physiological measurement of vascular placental function.

Objectives: To correlate UV blood flow with gestational age (GA) and foetal weight (FW) in a cohort of normal pregnant Nigerian women.

Materials and Methods: 2,247 women with normal singleton pregnancy between 20 – 40 weeks were included in this study, which was conducted between May 2020 – October 2022, in Bayelsa State, South-South Nigeria. The women had ultrasound assessment of UV blood flow and foetal biometric parameters and weight. Data was analysed using SPSS version 25, associations between categorical variables and between categorical and continuous variables were assessed using chi square and t-test, respectively, with p-value <0.05 considered statistically significant. Correlation analysis was done, and presented in tables and charts.

Results: There was a strong linear correlation between UV blood flow volume and GA (correlation coefficient, ɼ= 0.95; p=0.001), FW (ɼ=0.81; p=0.001), foetal biparietal diameter (BPD) (ɼ=0.88; P=0.001) and abdominal circumference (AC) (ɼ=0.75; P=0.001). Conversely, UV blood flow volume/FW showed a strong inverse relationship with FW (ɼ=- 0.73; p = 0.001), and a weak inverse relationship with GA (ɼ=- 0.36; p = 0.001).

Conclusion: UV blood flow increases with advancing gestation and FW. The increase in UV blood flow in later gestation is however surpassed by the increase in FW, resulting in a reduction in UV blood flow volume per unit FW in the third trimester. The linear increase in UV blood flow volume with foetal BPD and AC suggests that these three parameters could be used in combination to estimate both GA and FW.