The relationship of fetal eye movements to non-stress test results

This study was designed to correlate ultrasound-observed fetal eye movements with fetal heart rate reactivity to determine its potential role in fetuses with persistent non-reactivity.

A total of 104 non-stress tests (NSTs) were evaluated in 62 patients referred for fetal surveillance for standard antepartum indications. Ultrasound-observed eye movements, assessed during portions of these NSTs, were categorized as negative (0), intermittent (1-5/min), or rapid (> or = 6/min).

Of the NSTs, 97 were reactive and seven were non-reactive. All studied fetuses were apparently healthy, as the seven patients with persistently non-reactive NSTs had biophysical profile scores of 8/10. During the NSTs, 120 reactive portions and 81 non-reactive portions were evaluated for ultrasound-observed eye movements. During reactive portions, eye movements were negative 19% of the time, intermittent 24% of the time and rapid 56% of the time. During non-reactive portions, eye movements were negative 84% of the time, intermittent 7.8% of the time and rapid 7.8% of the time. All fetuses demonstrating eye movements during non-reactive periods became reactive shortly thereafter, and all of the seven persistently non-reactive fetuses displayed negative ultrasound-observed eye movements throughout the entire observation period.

Healthy fetuses display a strong relationship between non-reactive heart rate tracings and absent or diminished eye movements, consistent with quiet sleep. Conversely, reactive periods are associated with a high incidence of rapid eye movement. Further study is needed in fetuses documented to be hypoxic.