Fetal internal carotid and umbilical artery blood flow velocity waveforms as a measure of fetal well-being in intrauterine growth retardation.

Maximal flow velocity waveforms were recorded on one occasion from the umbilical artery (UA) and fetal internal carotid artery (ICA) in 240 normal pregnancies and 44 cases of intrauterine growth retardation between 26 and 39 wk of gestation. In normal pregnancy the mean UA pulsatility index (PI) decreased from 1.14 (SD: +/- 0.13) at 26-27 wk of gestation to 0.78 (SD: +/- 0.15) at 38-39 wk. The corresponding decrease in ICA PI was from 1.63 (SD: +/- 0.19) to 1.31 (SD: +/- 0.21). Mean values of UA PI for normal pregnancies were linearly related to gestational age; for ICA PI this relation appeared to be quadratic. Normal limits according to age were constructed by estimated means +/- 2 SD. In intrauterine growth retardation, the UA PI was increased (greater than 2 SD) in 80% of cases, ICA PI was reduced (greater than 2 SD) in only 45%. The outcome of fetuses with intrauterine growth retardation, as expressed by fetal heart rate abnormality, Apgar score at 1 min, and umbilical cord pH, was significantly related to the UA PI but not to the ICA PI.