Absent and reversed UA end-diastolic blood flow is usually a poor prognostic sign. However, in 19 fetuses evaluated in the Fetal Diagnosis and Treatment Unit, we observed an unusual pattern of intermittent, significantly decreased, or reversed UA blood flow that coincided with a demonstration of fetal hiccuping. No evidence of cardiac arrhythmia, heart failure, or uteroplacental dysfunction was found in these fetuses. With one exception, all Doppler evaluations were otherwise normal. A potential mechanism of intermittent fetal UA blood flow reversal is discussed.