Blink-startle reflex habituation in 30-34-week low-risk fetuses

OBJECTIVE: To investigate whether the blink-startle reflex (BSR) is a good marker of habituation to vibroacoustic stimulation in healthy preterm fetuses. MATERIALS AND METHODS: A total of 22 women with uncomplicated pregnancies at 30-34 weeks participated in the study. Vibroacoustic stimulus was repeatedly applied to the maternal abdomen above the fetal head for a period of 2 s every 10 s. Fetal eye tightening monitored by ultrasound within 2 s of the stimulus was considered a positive response. The habituation rate was defined as the number of stimuli applied before the fetus stopped responding to two consecutive stimuli. Results were compared using the Mann-Whitney U-test. RESULTS: All 22 fetuses showed habituation at a rate that varied from 1 to 9 (mean 4.2+/-1.8). CONCLUSION: BSR is a good marker of habituation in preterm fetuses. Further study is needed to ascertain whether abnormal BSR habituation could be a sign of fetal distress.