Fetal middle cerebral artery Doppler in late-term pregnancy: a predicting factor for failed induction of labor

Intra-observer variability of Doppler measurements in umbilical artery (UA) and middle cerebral artery (MCA) in uncomplicated term pregnancies

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.

Ultrasound Probe Pressure on the Maternal Abdominal Wall and the Effect on Fetal Middle Cerebral Artery Doppler Indices

Background and objectives: Doppler ultrasound of umbilical and fetal vessels is useful for monitoring fetal well-being, fetal anemia, intrauterine growth retardation, and other perinatal outcomes. The adverse perinatal outcome and circulatory changes can be reflected in fetal Doppler studies. The aim of this study was to evaluate the effect of increased pressure exerted on the maternal abdominal wall during routine ultrasound on the middle cerebral artery (MCA), resistance index (RI), pulsatility index (PI), and peak systolic velocity (PSV). Materials and Methods: A prospective study was conducted, in which we included 40 pregnant women between 24 + 0 and 41 + 3 gestational weeks (GW), with singleton pregnancies, without any associated pathologies, undergoing routine US examination. We recorded the flow velocity waveforms in the MCA, and we measured the RI, PI, PSV, and the applied pressure on to the maternal abdominal wall-needed for a proper evaluation of MCA. We then repeated the same measurements at two different higher pressure levels, at the same time having a proper image of the targeted vessel. Results: We found significant differences for the PI and RI levels with an increase in abdominal pressure (median PI 1.46, 1.58, and 1.92, respectively; median RI 0.74, 0.78, and 0.85, respectively; p < 0.05), for both PI and RI. At the same time, we found no significant differences for PSV in the studied group in relationship with increase in abdominal pressure (median PSV 39.56, 40.10, and 39.70, respectively; p > 0.05). Conclusions: The applied abdominal pressure by the examiner's hand, during routine US scan in pregnancy, can modify the MCA parameters of blood flow resistance (PI and RI) when measured by Doppler US, thus influencing the diagnostic accuracy in a series of pregnancy associated pathologies, such as chronic fetal distress (CFD) or intrauterine growth restriction (IUGR).