Objective: To evaluate the intra-observer variability of the middle cerebral artery (MCA) and umbilical artery (UA) Doppler measurement taken under optimal conditions in term, uncomplicated pregnancies.
Methods: A prospective study on uncomplicated singleton term pregnancies was performed. Multiple Doppler measurements were taken in the MCA and the UA by one examiner. Intra-rater agreement was calculated. Doppler indices were correlated to fetal biometric parameters and to gestational age.
Results: One hundred patients were recruited. MCA indices were found to have the highest strength of intra-rater/observer agreement (K = 0.888) versus only a "good" agreement for UA pulsatility index (PI) (K = 0.755).The MCA-PI was significantly correlated with BPD (r = -0.198, p = .047), EFW (r = -0.241, p = .01) and birthweight (r = -0.208, p = .03). A statistically significant decrease was found in the MCA PI (r = -.422, p < .001) and in the CPR (r = -0.444, p < .001) with advancing pregnancy, between 37 and 42 weeks gestation. The UA PI did not change significantly (p = .099) during this period.
Conclusions: MCA PI measured at term is reproducible with a high ICC. MCA PI significantly decreases with advancing gestation at term. No correlation was found between Doppler measurements and time to delivery.
Keywords: Doppler; middle cerebral artery; pulsatility index; umbilical artery.