The effect of fetal heart rate on the peak systolic velocity of the fetal middle cerebral artery.
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).
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.
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).
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.
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Swartz, AE; Ruma, MS; Kim, E; Herring, AH; Menard, MK; Moise, KJ
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