Umbilical Artery Pulsatility Index Values Research Articles

Fetal ductus venosus flow velocity waveforms and maternal serum AFP before and after first-trimester transabdominal chorionic villus sampling.

Doppler flow velocity waveform recording in the fetal ductus venosus and umbilical artery as well as maternal blood sampling for serum alpha-fetoprotein (MSAFP) was performed before and after transabdominal chorion villus sampling (TACVS) in 36 women of advanced maternal age (> or = 36 years). Gestational age ranged between 11 and 13 weeks. No chromosomal anomaly was detected. No statistically significant difference was observed in ductus venosus velocity parameters or in the umbilical artery pulsatility index (PI) before and after CVS in 35 women with a normal pregnancy outcome. One case resulted in fetal loss. Post-CVS median MSAFP levels at 12 weeks (25 kIU/l) and 13 weeks (35 kIU/l) were significantly higher than pre-CVS levels. In three cases, post-CVS MSAFP levels were higher than 600 kIU/l, correlating with feto-maternal transfusions of approximately 1.0-1.4 ml, i.e., of around 40 per cent of feto-placental blood volume. One of these cases displayed absence of fetal peripheral blood flow velocities and fetal bradycardia following TACVS, resulting in fetal loss 1 week later. The remaining two cases had a normal pregnancy outcome, but showed a more than 50 per cent reduction in ductus venosus velocity after TACVS, whereas umbilical artery PI remained unchanged. However, similar velocity changes were associated with only small feto-maternal transfusions. Umbilical artery PI values remained unchanged.

Correlation of Doppler and placental immunohistochemical features in normal and intrauterine growth-retarded fetuses.

The aim of this study was to correlate and compare Doppler and anatomical placental findings obtained from 48 normal and 35 intrauterine growth-retarded (IUGR) fetuses. The IUGR group consisted of 19 fetuses from pregnancies complicated by pre-eclampsia and 16 from healthy mothers. Color Doppler evaluation of umbilical, spiral and uterine arteries was performed. Placental specimens from both normal and growth-retarded fetuses were obtained at the time of delivery. Placental specimens were evaluated using histochemical and immunohistochemical techniques. A progressive decrease in the pulsatility index was observed in umbilical, spiral and uterine arteries throughout pregnancy in the normal-growth fetuses. High umbilical artery pulsatility index values were obtained in 29 out of the 35 growth-retarded fetuses, six of them showing absent or reversed end-diastolic umbilical artery flow pattern. A total of 13 IUGR fetuses showed high resistance uterine artery flow velocity waveforms. Increased pulsatility index values were obtained from the spiral arteries of 16 growth-retarded fetuses. Abnormal histological and histochemical placental patterns were observed in all the growth-retarded fetuses with umbilical artery Doppler abnormalities. The presence of a peculiar dendritic cell subpopulation, strongly resembling the Langerhans cells, expressing the HLA-DR+/CD1+ phenotype, was detected in all growth-retarded fetuses, whether there was maternal pathology or not. Our data show uterine and spiral artery data as being ineffective in the monitoring of IUGR fetuses. The placental extracellular matrix seems to play an important role in the regulation of the umbilical circulation. The presence of CD1+ cells as a sign of a possible immunological mechanism in the pathogenesis of the intrauterine growth retardation is discussed.

Umbilical vein pulsations: A physiologic finding in early gestation

The purpose of this study was to establish the incidence of umbilical vein pulsations in normal early pregnancies and to evaluate whether these pulsations are related to Doppler-measured vascular resistances in umbilical artery or central venous flow patterns. We performed a cross-sectional study on 257 uneventful pregnancies at 7 to 16 weeks of gestation by means of transvaginal color and pulsed Doppler ultrasonography. Blood flow velocity waveforms were recorded from the umbilical artery, umbilical vein and, in 48 cases, also from fetal inferior vena cava. Pulsations in the umbilical vein were evidenced in all cases until 8 weeks. From this gestational age on pulsations progressively disappeared, becoming completely absent at greater than or equal to 13 weeks. The incidence of pulsations in the umbilical vein was unrelated to umbilical artery pulsatility index values, the incidence of absent end-diastolic flow in umbilical artery, and fetal heart rate. In the inferior vena cava, reverse flow during atrial contraction was significantly higher (p less than or equal to 0.002) in cases with umbilical vein pulsations than in those cases without pulsations at a similar gestational age. Pulsations in the umbilical vein are physiologically present during the first trimester of pregnancy and seem to be related to inferior vena cava flow patterns.

Can umbilical artery pulsatility index predict the outcome of fetuses with structural heart disease?

Umbilical artery Doppler waveforms have been suggested to demonstrate diminished end-diastolic velocities in anomalous fetuses. We evaluated 11 fetuses with antenatally diagnosed congenital heart disease (CHD) and compared them to a normal population. Fetuses with CHD were studied once each and ranged in age from 19 to 32 weeks gestation. Eight had normal chromosomes, and three were aneuploid. The pulsatility index (PI) was elevated (above the 90th percentile for gestational age) in 3/11 CHD fetuses (P = NS). Elevated PI did not discriminate well between those with fatal and nonfatal lesions. Although all three fetuses with elevated PI had fatal disease, five of eight fetuses with fatal anomalies had normal PI values. We conclude that, while umbilical artery PI values were elevated in a subgroup of affected fetuses, this was not clinically helpful.

The effect of indomethacin on the pulsatility index of the umbilical artery in human fetuses

Pulsed and continuous-wave Doppler ultrasonography was used to assess blood velocities in the ductus arteriosus and the pulsatility index of the umbilical artery in 20 fetuses (1 pair of twins and 18 singletons) at 23 to 33 weeks' gestation during maternal indomethacin therapy for preterm labor or polyhydramnios. There was no statistically significant difference in the pulsatility index of the umbilical artery during maternal indomethacin treatment (mean +/- SD, 1.11 +/- 0.20) when compared with baseline values (1.12 +/- 0.19) in all 20 fetuses studied. An increase in the peak systolic and diastolic blood velocities in the ductus arteriosus consistent with ductal constriction was noted in 9 fetuses. Analysis of the umbilical artery pulsatility index values before and during indomethacin in this subgroup of fetuses failed to reveal a statistically significant change (1.12 +/- 0.19 vs. 1.11 +/- 0.20). Indomethacin therapy does not influence the pulsatility index of the umbilical artery at the gestational ages studied.

Feto-placental circulatory competence

Doppler assessment of the pulsatility index (PI) of umbilical artery blood velocities offers promise as a simple, non-invasive method for early diagnosis of placental failure. The present report identifies the hemodynamic factors determining this PI, based on current knowledge of feto-placental physiology. It is postulated that the umbilical artery PI is mainly determined by the ratio of capillary to arterial resistances in the fetal placental circulation. However, the biological PI variations on a minute by minute basis are caused by short-term variations in blood pressure pulsatility. The ratio of resistances declines markedly with advancing pregnancy, indicating that the site of predominant resistance determining the volume of placental blood flow gradually migrates from the peripheral capillary to the arterial compartment. After 28 wk of gestation, umbilical artery PI values decrease below 1, reflecting the normal reserve capacity of the functional capillary bed of the placenta. PI values above 1 in the last trimester reflect a critical enhancement of placental capillary resistance, which must impede blood flow to functional chorionic villi. It is concluded that this Doppler technique may provide a simple method for clinical assessment of placental circulatory competence.