Reference Ranges of Doppler Indices in the Fetal Middle Cerebral Artery according to Gestational Age

Park, Yong Won; Cho, Jae Sung; Kwon, Hye Kyung; Kim, Young Han; Lee, Chang Hee

Abstract

OBJECTIVES
To investigate the "brain sparing effect", a paradoxical increase in fetal cerebral perfusion in pregnant women with uteroplacental insufficiency through fetal middle cerebral artery(MCA) waveform analysis, and to construct new reference ranges for fetal MCA Doppler flow velocity resistance indices in nomal preganacies to be used in the assessment of fetal well-being.
MATERIALS AND METHODS
The subjects were selected from pregnant women receiving antenatal care at Severance Hospital between March 1996 and December 1999. Fetal MCA reference resistance index range according to gestational age were obtained through routine Doppler velocimetry for 4621 normal pregnant women between 24-42 gestational weeks. Those manifesting multiple pregnancy, Diabetes Mellitus, drug abuse, chronic hypertension, fetal congenital anomaly, fetal growth restriction(FGR) with discrepencies of more than 7days and pregnancies complicated by pregnancy induced hypertension (PIH) were excluded. Additionally, the fetal MCA hemodynamic changes were compared for 140 pregnant women with FGR or PIH. The normal ranges for fetal MCA Doppler resistance indices were expressed as mean+/-SD, and a comparative analysis between the PIH or FGR group and the normal control group was performed. Statistical analysis was done using the SPSS 8.0 program, t-test and the Pearson correlation. RESULT: The fetal MCA doppler flow resistance indices for normal pregnancies were 0.77+/-0.006 at 24 weeks and 0.79+/-0.006 at 28 weeks, demonstrating a statistically significant increase(p<0.05). At 40 weeks the index was 0.71+/-0.009 showing a significant decrease after 28weeks(p<0.05). There was a tendency for the resistance index to be lower in the PIH/FGR group compared to the normal controls.
CONCLUSION
Constructing a normal reference resistance index range for fetal MCA flow is of high clinical value with regards to predicting fetal well being and understanding the hemodynamics of fetal cerebral perfusion.