The Effect of Fetal Heart Rate on the Peak Systolic Velocity of the Fetal Middle Cerebral Artery

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Abstract

OBJECTIVE:

To estimate the effect of an increase in the basal heart rate of the fetus on the middle cerebral artery peak systolic velocity (MCA-PSV).

METHODS:

This was a prospective longitudinal cohort. Patients between 14 and 36 weeks of gestation were enrolled (N=66). Ultrasound examinations were performed monthly. MCA-PSV measurements were assessed at 0-degree angle of insonation at basal fetal heart rate and after application of vibroacoustic stimulation.

RESULTS:

A total of 514 MCA-PSV measurements were obtained in 66 fetuses. No difference in fetal heart rate before and after vibroacoustic stimulation was noted before 27 weeks of gestation. A significant increase in fetal heart rate after vibroacoustic stimulation was detected from a mean±standard deviation gestational age of 27.1±1.3 weeks onward. A significant decrease in the MCA-PSV was noted between before vibroacoustic stimulation and after vibroacoustic stimulation measurements for examinations 3,4, and 5 (P<.001 for all).

CONCLUSION:

Acceleration of the fetal heart rate in the third trimester is associated with a decrease in the middle cerebral artery peak systolic velocity. Assessment of the MCA-PSV for the detection of fetal anemia, particularly in the third trimester, should be undertaken during a period of baseline fetal heart rate to avoid the potential of a false-negative result.

LEVEL OF EVIDENCE:

II

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