Noninvasive assessment of fetal aortic blood flow in normal and abnormal pregnancies.

Abstract

Fetal blood flow measurements have a good capacity to predict unfavorable fetal outcome, especially chronic distress accompanied by IUGR. The descending thoracic aorta is of particular interest in these studies and the results reflect peripheral vascular resistance, both in the fetal placental circulation and in fetal abdominal and peripheral areas. A pathologic finding in blood velocity waveforms, especially an absent end-diastolic velocity, seems to be an early and consistent alteration that precedes the occurrence of a pathologic CTG pattern by at least several days. According to our experience, the main benefit of fetal blood flow studies is in differentiation between IUGR fetuses, in which growth retardation is accompanied by some degree of fetal hypoxia, and those cases in which the small size does not signify an immediate threat to fetal well-being. Nevertheless, there are still a number of diagnostic and practical problems. The individual fetal capability to tolerate impaired fetal placental circulation and hemodynamic redistribution is variable. Hence, it is impossible to make clinical decisions based only on hemodynamic findings; we also need diagnostic support from other methods (evaluation of fetal structures by ultrasound, CTG registration, rapid fetal karyotyping, and fetal acid-base status). In some cases, pathologic blood velocity waveforms develop as soon as at weeks 24-27, and because of the lack of reliable therapeutic methods to improve fetal condition, the selection of an ideal time of delivery is often a compromise between threatened fetal asphyxia and prematurity.(ABSTRACT TRUNCATED AT 250 WORDS)