Fetal startle response observed under ultrasonography: a good predictor of a reassuring biophysical profile

To correlate the vibroacoustic stimulus-evoked fetal startle response observed under ultrasonography with the subsequent biophysical profile (BPP) score.

Vibroacoustic stimulation was applied under ultrasound observation to gravidas who had a nonreactive fetal heart rate in the first 10 minutes of monitoring. Fetal startle response was defined as a sudden movement of fetal extremities in the 2 seconds following stimulus. Subsequently, nonstress testing was completed and a BPP performed on all women who required vibroacoustic stimulation. The presence or absence of a fetal startle response was compared with the observed BPP score.

Two hundred tests were performed at 35.3 +/- 3.7 weeks. After the vibroacoustic stimulation, 70% of the nonreactive tracings became reactive. Mothers perceived the fetal startle response after vibroacoustic stimulus in 93% of cases. All cases with a fetal startle response after a vibroacoustic stimulation had a subsequent BPP score of 8 or more (negative predictive value of 100%). In addition, all patients with a nonreassuring BPP score were in the group of patients with absent fetal startle response. However, the positive predictive value of an absent fetal startle response for a subsequent BPP score of 6 or less was only 10%.

This preliminary study suggests that the fetal startle response predicts a BPP score equal to or greater than 8. After the availability of larger studies supporting these findings, this test could be used as a rapid antepartum test to predict fetal well-being.