Vibroacoustic stimulation of the fetus using a conventional mechanical alarm clock

Objective: For more than 20 years, vibroacoustic stimulation testing (VAST) using an artificial larynx has been used worldwide when fetal heart rate m onitoring produced patterns with absent or very low variability. In additio n to the artificial larynx many other appliances have been used to stimulat e a seemingly dormant fetus, but these have rarely been evaluated properly. In this study we tried to evaluate the use of standard mechanical wind-up alarm clocks for VAST. Methods: VAST with an alarm clock was performed successfully in 80 women wi th normal pregnancies from 36 weeks to term. It was tested by placing the a larm clock on the maternal abdomen just above the fetal head or on the cont rolateral side of the maternal abdomen to see whether position made any dif ference and whether coupling with ultrasound gel applied between the alarm clock and the maternal abdomen would affect the degree of fetal reaction to VAST as expressed in heart rate acceleration. Similarly, the effect of the alarm clock VAST on subjective and objective fetal movement patterns as re gistered by kinetocardiotocotraphy (K-CTG) in addition to heart rate patter ns was investigated. Results: All fetuses showed heart rate acceleration, an increase in heart v ariability, and increase in movement patterns in the 6 min after the applic ation of alarm clock VAST. No statistically significant difference was foun d which would favor a particular placement of the alarm clock on the matern al abdomen or the use of ultrasound coupling gel. When K-CTG was performed, patient-perceived fetal movements as expressed with an event marker showed agreement with the machine-registered movements only when patients could s ee the tracing during registration and no accordance when the K-CTG was tur ned toward the wall during registation. Conclusion: In keeping with the ALARA principle a conventional wind-up alar m clock appears to be an inexpensive and effective alternative to the elect rolarynx.