CHANGES OBSERVED IN DOPPLER STUDIES OF THE FETAL CIRCULATION IN PREGNANCIES COMPLICATED BY PREECLAMPSIA OR THE DELIVERY OF A SMALL-FOR-GESTATIONAL-AGE BABY .1. CROSS-SECTIONAL ANALYSIS

The aim of this study was to compare changes in Doppler ultrasound studies of the fetal circulation in normal pregnancies with a group of pregnancies complicated by proteinuric pregnancy-induced hypertension (PPIH), delivery of a small-for-gestational-age (SGA) baby, or both. A total of 167 uncomplicated pregnancies with a term delivery of an appropriately grown baby (AGA) were used to define the normal range. Altogether, 123 high-risk pregnancies with a known outcome constituted the study group. A color duplex ultrasound machine was used to perform biometry and fetal Doppler studies. Measurements obtained from the fetal circulation included the umbilical artery (UA) pulsatility index (PI), the middle cerebral artery (MCA) PI and time-averaged velocity (TAV), the thoracic aorta (AO) PI and TAV. In addition, the ratio between the MCA PI and UA PI, the MCA PI and the AO PI, and the product of the MCA PI and AO TAV were used in the analysis. A total of 105 pregnancies had a complicated outcome. They were divided into three categories: PPIH only (pregnancies complicated by PPIH with the delivery of an AGA fetus, n = 17), SGA only (delivery of an SGA baby, with no evidence of PPIH, n = 55), and PPIH + SGA (pregnancies complicated by pre-eclampsia and delivery of an SGA baby, n = 37). The PPIH + SGA group represented true clinical intrauterine growth retardation. Cross-sectional reference ranges were created using the observations from the normal group. z-scores (standard deviation from the mean of the normal range) of the last observations made before delivery were calculated for each of the vessel velocimetry measurements and ratios. The statistical significance of z-score values was calculated using analysis of variance. The MCA and UA PI values showed the greatest deviation for any single-vessel parameter. The ratios of fetal Doppler indices (MCA/UA PI ratio, MCA/AO PI ratio and the MCA PI/AO TAV index) demonstrated greater deviation from normal than any individual vessel. The UA Pl z-score for PPIH + SGA delivering < 34 weeks gestation (2.92) was significantly greater than the z-score for PPIH + SGA delivering greater than or equal to 34 weeks (1.20, p < 0.05). Fetal Doppler indices, in particular ratios that include measurements obtained from the cerebral circulation, help in the recognition of the small fetus that is growth-retarded. At term, evidence of fetal hemodynamic redistribution may exist in the presence of a normal umbilical artery PI. Fetal Doppler indices provide information that is not readily obtained from more conventional tests of fetal well-being. It therefore has an important role to play in the management of the growth-retarded fetus.