Changes in placental blood flow in the normal human fetus with gestational age

We assessed fetoplacental blood volume flow and placental resistance prospectively with Doppler sonography in 74 normal human fetuses of 19 to 42 wk gestation to determine the changes in placental perfusion with gestational age. Placental blood volume flow was assessed from the umbilical vein as the product of the mean flow velocity integral and the cross-sectional area of the umbilical vein. Placental resistance was assessed as the ratio of maximum systolic and minimum diastolic blood flow velocities from an umbilical artery. Umbilical vein blood volume flow increased exponentially (r = 0.86) with gestational age from 19 wk to term, and did not decrease in postdate fetuses. Umbilical vein blood volume flow increased linearly with fetal weight (r = 0.77), although volume flow per unit body weight changed little with gestational age. Umbilical artery velocity ratio decreased progressively, indicating diminishing placental resistance with gestational age, but did not correlate closely with umbilical vein blood volume flow. We submit that fetoplacental blood volume flow can be readily calculated directly from the umbilical vein with Doppler ultrasound and may provide a better index of placental perfusion than the umbilical artery velocity ratio.

Hypoxic acidemia, hyperviscosity, and maternal hypertension do not affect the umbilical arterial velocity waveform in fetal sheep

The effect of hypoxic acidemia, hyperviscosity, and maternal hypertension on the umbilical arterial velocity waveform was studied in 23 chronically catheterized fetal sheep. Fetal hypoxic acidemia induced by lowering the maternal inspired oxygen concentration (n = 7) caused no change in the ratio of systolic/diastolic blood velocity even when fetal arterial pH was as low as 6.8. Fetal blood hyperviscosity (n = 7) induced by exchange transfusion with packed maternal blood cells increased placental vascular resistance by greater than or equal to 50% but had no significant effect on the systolic/diastolic ratio. Similarly, maternal hypertension induced by intravenous infusion of angiotensin II to the ewe (n = 9) did not affect the systolic/diastolic ratio despite a 50% increase in maternal arterial blood pressure. We conclude that umbilical arterial velocity waveform abnormalities observed in growth-restricted human fetuses are probably not a direct result of fetal hypoxemia or hyperviscosity or maternal hypertension.

[The measurement of umbilical artery flow velocity waveforms in normal late pregnancy by Doppler ultrasound]

Doppler ultrasound was adopted in a study of fetal umbilical artery flow velocity waveforms in 81 cases of late pregnancies (28-41 gestational weeks). The peak systolic/end-diastolic ratio (A/B) and the Pourlot index were used as indices for assessing placental resistance. Both the A/B ratio (2.34 +/- 0.44) and Pourlot index (0.56 +/- 0.07) decreased while the gestational week was increasing, and they had a good correlation with the gestational week (r1 = -0.90, r2 = -0.93). The results indicated that the placental resistance became lower when the gestational week was increasing. This method has been documented a useful noninvasive technique for the exam of placental resistance.

[Measurement of fetoplacental blood flow (resistance index) during labor with meconium stained amniotic fluid using the doppler technic]

The blood flow in the fetoplacental circulation (umbilical artery) was examined by the Doppler technique in 42 labouring women with the meconium stained amniotic fluid. Ultrasound examination in the phase of cervical dilatation of 2-5 and 6-9 cm by the Doppler technique before and during contraction was carried out in each woman. Flow velocity wave-forms (FVW) of the umbilical artery were analysed by using the resistance index (RI). The ultrasonic apparatus Kranzbuhler ADR 8130 was used for measuring. The control group consisted of 54 labouring women with a clean, milky amniotic fluid. All resistance index (RI) mean values with the meconium amniotic fluid. All resistance showed a statistically significant decrease when compared to the group with the milky amniotic fluid (T = 5.91 p less than 0.01; t = 4.57 p less than 0.01; t = 5.73 p less than 0.01 t = 3.19 p less than 0.01). They probably are an indicator of the compensatory mechanism of the fetus.

[Does vascularization of the fetal placenta modify end-diastolic blood flow velocity in umbilical arteries? A histometric contribution to the validation of Doppler ultrasound]

The foetal intravillous blood volume was approximately determined in 90 cases, using placental histiometry post partum. This was compared with the Doppler sonographic flow patterns in the umbilical arteries determined during the last week ante partum. A direct dependence was seen: The larger the peripheral vascular tree of the placenta fetalis, the lower the resistance against the blood flow in the umbilical artery, i.e. the higher the enddiastolic blood flow velocities and vice versa. There is a highly significant correlation between the foetal intravillous blood volume and the foetal risks of Caesarean section performed, because of intrauterine asphyxia, growth retardation or reduced foetal outcome.

Early warning of fetal compromise--absent end diastolic flow?

This report deals with the use of a relatively new investigative technique (Doppler ultrasound) in the management of a case of early onset pre-eclampsia and discusses the benefit of this new technique over conventional methods of fetal monitoring.

Umbilical artery velocimetry in insulin dependent diabetes mellitus (IDDM) pregnancies

Seven hundred and sixty seven Doppler umbilical artery velocity waveform analyses were performed in 108 pregnant insulin-dependent diabetes mellitus (IDDM) women. No significant correlation between mean third trimester systolic to diastolic (S/D) ratio and either mean blood glucose (r = 0.19) or glycosylated hemoglobin levels (r = 0.28) was found. Mean second and third trimester S/D ratios differed significantly in patients with or without vascular disease (P less than 0.05). Furthermore, women without vasculopathy who demonstrated an elevated S/D developed preeclampsia and delivered appropriate for gestational age infants while patients with vascular disease or chronic hypertension and elevated third trimester S/D (greater than 3) delivered intra uterine growth retarded (IUGR) infants. Moreover, in most of the latter group elevated S/D ratios were recorded in the second trimester prior to ultrasound documentation of IUGR. Our data suggest that in the absence of vasculopathy normal fetal placental resistance can be expected in most pregnancies complicated by diabetes. Patients with vasculopathy are at higher risk for fetal IUGR, which may be identified by early umbilical artery velocimetry.

Characteristics of the umbilical artery velocity waveform as function of measurement site

In 30 uncomplicated singleton pregnancies, varying in duration between 24 and 40 weeks, the variability of the flow velocity waveform (FVW) along the course of the umbilical artery was investigated. Blood flow velocities were recorded at 4 locations in the vessel: within the fetal abdomen, 0-5 cm from the origin of the umbilical cord, in the free-floating part, and 0-5 cm from its insertion in the placenta. From the Doppler signals recorded, the pulsatility index (PI) and a parameter for the frequency distribution index (FDI) were calculated. PI values differed among the locations, but no unequivocal tendency could be demonstrated. Statistical analysis, including multiple regression analysis for maternal and menstrual age and fetal heart rate, showed no significant difference in PI and FDI values for any of the 4 locations. It can be concluded that in uncomplicated pregnancies, possible changes in FVW (quantified by PI) along the course of the umbilical artery have no clinical relevance. Therefore, standardization for the sampling site when measuring PI in this vessel seems to be unnecessary.

Normal umbilical artery Doppler sonography does not exclude fetal distress

Umbilical artery Doppler sonography is advocated as a method for fetal surveillance. Two cases of fetal distress caused by fetal anemia of non-immune origin are presented. In both cases a normal pulsatility index of the umbilical artery was found. It is emphasized that normal umbilical artery Doppler sonography does not exclude fetal distress.

[Diagnosis and therapy of occlusion caused by thromboembolism in a premature infant using digital subtraction angiography]

A neonate born after 35 weeks' gestation developed thrombosis of the right external iliac artery after removal of an umbilical artery catheter. Digital subtraction angiography was utilized to demonstrate the site of obstruction and the effect of fibrinolytic therapy with streptokinase.

Persistent sciatic artery: a case report

Persistence of the embryonic sciatic artery is a rare vascular anomaly with only 52 documented cases, of which only 19 had angiographic studies. We describe a patient with angiographic demonstration of persistence of a left sciatic artery associated with arterial anomalies of the opposite limb. The embryology radiological findings and clinical significance are discussed.

False diagnosis of persistent fetal circulation caused by misplacement of umbilical artery catheter

We have described two cases in which persistent fetal circulation was mistakenly diagnosed because umbilical artery catheters were placed in too high a position. In one case, repeated doses of tolazoline were given unnecessarily. While high placement of umbilical artery catheters is commonly accepted, misplacement may not always be apparent on routine AP chest films taken to confirm catheter positioning.

A human umbilical cord with four arteries

An unusual case of a newborn infant with four umbilical arteries is presented. Multiple catheterizations revealed that triplication of the right umbilical artery was responsible. There were no associated malformations, and follow-up at 9 months of age revealed age-appropriate growth and development. This case extends the spectrum of observable umbilical artery anomalies.

Dystrophic calcification in obliterated umbilical artery

Evidence is presented that calcification may occur within the horizontal pelvic portion of the obliterated umbilical artery and that the finding may be visible on abdominal radiographs.

The "inverted V" sign of pneumoperitoneum

On the supine radiograph, an inverted "V" may be seen over the pelvis in a patient with pneumoperitoneum. While in infants this is produced by the umbilical arteries, in adults it appears to be created by the inferior epigastric vessels.

Sirenomelia. Angiographic demonstration of vascular anomalies

A 1,730-g infant with severe caudal regression syndrome (sirenomelia) died shortly after delivery, after a 34-week gestation. Autopsy findings included multiple skeletal anomalies, renal agenesis, amnion nodosum, and a single lower extremity. Postmortem arteriography demonstrated a persistent vitelline artery and documented the vascular pattern within the lower extremity. To our knowledge, angiographic demonstration of the lower limb vascularity has not been described previously in sirenomelia. The angiographic findings support the pathogenetic concept of limb bud fusion and malrotation of the limb in sirenomelia after damage to the posterior axis mesoderm in early embryonic life. Postmortem arteriography is an inexpensive, retrievable, and easy means of documenting vascular anomalies in the fetus or infant with multiple congenital abnormalities.

Umbilical vascular catheters: localization by two-dimensional echocardio/aortography

Umbilical vascular catheters are often necessary in the care of critically ill neonates. Position of the catheter tip is usually determined by roentgenography. Location of the umbilical arterial or venous catheter was determined by 2-dimensional echocardio/aortography in 55 consecutive infants and was compared to localization by thoraco-abdominal roentgenography. Most of the infants (76%) had respiratory distress syndrome or congenital heart disease. Echocaortographic localization of the umbilical arterial catheter correlated very closely (N = 50, sr = .90) with roentgenographic determination. For localization of the tip of the umbilical venous catheters, echocardiography was more accurate than roentgenography (employing contrast echocardiography for confirmation of cardiac chamber position). Two-dimensional echocardio/aortographic localization of the tip of indwelling umbilical vascular catheters is as accurate as roentgenography in the arterial system and more accurate than x-ray for umbilical venous catheters. Echocardio/aortography is superior to roentgenography (in localizing the catheter tip) because it 1) avoids ionizing radiation, 2) makes positioning of the patient unnecessary, 3) allows visualization of the catheter in relation to cardiovascular structures, and 4) may allow demonstration of intraarterial thrombo-emboli.

Umbilical artery catheterization in newborns. IV. Strain-gauge plethysmography for the diagnosis of catheter-related thrombo-embolism in the legs

Strain-gauge plethysmography was performed shortly after withdrawal of the catheter in 48 of 49 newborn ifnats who had undergone umbilical artery catheterization. Plethysmorgraphy was used to find a noninvasive method for diagnosing catheter-related thrombo-embolism in neonates. The results were compared with the findings at aniography. The method permits simultaneous measurements of the systolic blood pressure and of the resting and submaximal blood flow in both legs. Nine infants howed angiographic signs of total or partial occlusion in one leg, and 8 of them were investigated with plethysmorgraphy. The systolic blood pressure was signifcantly reduced in ifants with total and/or partial occlusion, but the blood flow was reduced only in infants with total occlusion. The peak flow after sugrasystolic occlusion was significantly otener delayed in infants with thrombo-embolism in the leg.

The risks of umbilical vessel catheterization in a neonatal intensive care unit

Five hundred and fourteen high-risk neonates who had indwelling umbilical catheters at the neonatal intensive care unit of the University of Benin Teaching Hospital were studied. of these 514 neonates, 122 (23.8%) had their catheters in-situ for longer than 24 h. Of the 122, fifty-four (44%) had positive bacterial cultures from their catheter tips. Seven (5.7%) and four (3.2%) of the 122 neonates studied developed septicaemia and necrotizing enterocolitis respectively. Catheterization for periods in excess of 48 h significantly increased the risk of bacterial colonization. Malposition of umbilical catheter tips include: insertion into the right portal vein (thirty-six cases); superior mesenteric vein (three cases) and the left atrium (four cases). The complications related specifically to the malposition were: air collection in the hepatic venous system (two cases); cardiac arrest (one case); necrotising enterocolitis (one case) and a case of blanching of the abdominal wall. Because of these complications, the indications for catheterization should be restricted to carefully selected patients and strict aseptic technique be adhered to during the procedure.

Single film retrograde umbilical aortography in the diagnosis of hypoplastic left heart syndrome with aortic atresia

Single film retrograde umbilical aortography was used successfully in confirming the diagnosis of hypoplastic left heart in three neonates. The method involves injecting Renografin 75% (1.25 cc/kg body weight) into the umbilical artery catheter according to the following sequence. First, the tip of the catheter is positioned at the level of the ductus arteriosus. The infant heart beats are then counted from one to three. The contrast media injection is begun manually on the count of one and an anterior-posterior chest film is taken on the count of three. Thus the film is taken one diastolic period after completion of the injection. The proper timing of the contrast media injection and filming is essential for obtaining a diagnostic film. This procedure was diagnostic in the three infants studied and eliminated the need of transferring two sick infants from affiliated hospitals.

An evaluation of the radiological signs of fetal death

Radiological investigation is warranted in the antenatal patient only if the findings are likely to influence future management. The major radiological signs of fetal death are gas in the fetus, overlapping of the cranial bones and Deuel's halo sign. Gas patterns in the portal and umbilical vessels are unique and pathognomonic. Deuel's halo sign would be found more commonly if the correct radiographic view was employed. Spalding's sign is of no value before 20 weeks or if the fetal head is subjected to pressure. Hyperflexion of the fetus more often indicates intra-uterine growth retardation than death in utero.