Fetal arterial redistribution indicating true umbilical cord knot

True umbilical cord knot often remains undiscovered prenatally due to a lack of characteristic clinical or ultrasound signs. We present a pregnancy with favorable outcome in which a non-stress test (NST) found non-reassuring fetal status. Abnormal Doppler blood flow patterns in the descending aorta and in the middle cerebral artery revealed fetal arterial redistribution with normal circulation in the umbilical artery despite a true cord knot. The benefit of fetal Doppler assessment is discussed. Increased aortic-cerebral ratio may reflect acute hypoxic compromise caused by the transitory constriction of the true umbilical cord knot with unrecognized morphologic and circulatory signs. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.