Changes in Doppler blood flow velocity in middle cerebral artery in response to airborne sound in low- and high-risk human fetuses.

Objective: To examine fetal auditory perception in low- and high-risk pregnancies in period from 27 to 31 weeks gestational age with the aim to establish diagnostic parameters in prenatal detection of the degree of hearing development in a fetus.

Methods: Method of prenatal hearing screening was applied on 80 women divided in two groups: Control group (C=22), consisted of pregnant women with low-risk pregnancies, and Experimental group (E=58), consisted of pregnant women with high-risk pregnancies (pregnancies with diagnosis of: preterm delivery, hypertension and/or intrauterine growth restriction (IUGR), diabetes). PHS was applied in period from 27 to 31 weeks gestational age. Brain circulation changes in fetal middle cerebral artery (MCA) caused by defined sound stimulus, as the indicator of fetal auditory reactions, were registered on Doppler ultrasound apparatus. After visualization of MCA, a sound stimulus was delivered. The stimulus consisted of one defined sound which is a digitally produced sound with the intensity of 90 dB, frequency range of 1500-4500 Hz, and duration of 0.2s (click) and it was presented only once. Measurements in observed artery were taken before (baseline) and after defined sound stimulation.

Results: Results showed that the absolute and relative difference in Pulsatility index (baseline and after sound stimulation) were greater for the high-risk group compared to the low-risk group (absolute difference: mean=0.36 vs mean=0.36) (relative difference: mean = ∼ 18% vs mean = ∼ 12%). When the low-risk group and the three high-risk group mean pairs were compared using multiple t-test, the diabetic group differed from the low-risk and two other high-risk groups; the low-risk and the two other high-risk groups did not differ from each other. Fetuses from pregnancies with diagnosis of diabetes demonstrated the most expressive reactibility and significantly higher absolute and relative changes of Pi values (absolute difference: mean=0.54, relative difference: mean=25.49%).

Conclusion: The values of Pulsatility index (Pi) registered by PHS in low- and high-risk pregnancies may be used as differential and diagnostic parameters in fetal auditory perception examination. Fetuses from pregnancies with diagnosis of diabetes demonstrated significantly higher absolute and relative changes of Pi values compared to other groups of examined fetuses.