Umbilical Artery Blood Flow Research Articles

Relationship between pitch value or S/D ratio of torsion of cord and fetal outcome

To evaluate whether applying pitch values at different positions of the umbilical cord or the umbilical artery blood flow systolic/diastolic (S/D) ratio measured by color ultrasound could forecast excessive torsion of cord and help in selection of the appropriate mode of delivery. This study included 184 pregnant women between 37 and 41 weeks of gestation and their neonates. We analyzed the umbilical cord's spiral distance, and the umbilical artery blood flow parameters at the cord's initial section, middle section and the section into the placenta. We also examined the fetal umbilical cord after birth, performed blood gas analysis of umbilical cord blood and recorded the neonatal Apgar score. Excessive torsion of cord diagnosed by ultrasound and in postnatal anatomy had the same rate of 91%. With lower pitch values (<2.0) and higher S/D ratios (>3.0), the possibility of fetal distress was increased, the neonatal Apgar score was decreased and umbilical blood pH values < 7.2 were more common. Pitch values and blood flow S/D ratios in different sections of the umbilical cord measured by color ultrasound could forecast excessive torsion of cord and have great significance in reducing the perinatal death rate caused by umbilical cord factors.

The persistent challenge of foetal heart rate monitoring

To analyse the reasons why foetal heart rate (FHR) monitoring failed to fulfil the initial expectations of unequivocally decreasing perinatal morbidity and mortality, and to summarize the most recent advances in this field. It is now clear that expectations towards FHR monitoring at the time of its introduction into clinical practice were unrealistic. Several pitfalls in FHR monitoring have been identified, and solutions established to avoid them. Correct use of FHR equipment and adequate tracing recording are as important as analysis and interpretation. New methods of computerized FHR analysis have been developed, and wide clinical validation of these is currently ongoing. More concrete guidelines on future research and development, as well as on regular training of healthcare professionals have been produced. FHR monitoring needs to be used with realistic expectations. Acquisition, storage and analysis of tracings according to available guidelines need to be guaranteed. Integration of data with foetal blood sampling and foetal ECG analysis during labour, and with umbilical artery blood flow analysis or the biophysical profile in the antepartum period, may further improve clinical decisions. Central monitoring stations and computer analysis are becoming more widespread and are currently undergoing wide clinical evaluation. Research, development and training need to take into account recent guidelines outlining the main issues in these fields.

288: Homeostatic implications for a relationship between placental corticotrophin-releasing hormone (PCRH) and umbilical artery blood flow in human pregnancy

The role of placental CRH in human fetal growth and parturition is well established. pCRH also is a potent vasodilator and may represent an important endocrine mechanism to maintain homeostasis within the fetal-placental unit. We recently reported that a higher uterine or umbilical artery resistance index (RI) is associated with increased risk of preterm delivery (Placenta 2009). The objective of the present study was to examine the association between pCRH concentrations and changes in umbilical artery resistance indices (UA RIs) across two time points in human gestation.

Modificaciones del flujo sanguíneo de las arterias uterina, umbilical y cerebral media fetal en preeclámpticas tratadas con parches de nitroglicerina

Objective To identify modifications in blood flow in uterine, umbilical and fetal middle cerebral arteries in preeclamptic patients treated with nitroglycerin patches. Method The sample consisted of 31 preeclamptic nulliparous patients with pregnancies of more than 25 weeks who attended the obstetric emergency service at the Dr. Urquinaona Central Hospital. The pulsatility index, resistance index and systolic/diastolic blood flow ratio of uterine, umbilical and fetal middle cerebral arteries were measured before treatment and after 24 and 48 h of treatment administration. Treatment consisted of 5 mg transdermal nitroglycerin patches, applied in the anterior thoracic and lumbar region of patients for 12 h (total time of 48 h). Results The pulsatility index, resistance index and systolic/diastolic blood flow ratio significantly decreased after the use of nitroglycerin patches (p<0.05). There were no significant modifications in the umbilical and fetal middle cerebral arteries at 24 and 48 h when compared with initial values (p=ns). There were no adverse effects. Conclusion Nitroglycerin patches decreased resistance to blood flow in the uterine arteries of preeclamptic patients without producing significant modifications in the umbilical and fetal middle cerebral arteries.

Sonographic Assessment of the Umbilical Cord

AbstractThe umbilical cord is crucially important feto-maternal unit, though very simple in structure while containing two arteries and one vein; it modulates blood flow conveyance between the fetus and placenta. Umbilical cord characteristics, such as cord length and thickness, number of vessels and their diameters, amount of Wharton's jelly, type of placental insertion, coiling and blood flow patterns are recognized contributors that may reveal increased risk for possible antenatal and perinatal complications. However, during the “routine” fetal anatomical survey, only the number of umbilical cord vessels is recorded in majority of antenatal centers. Thereafter, umbilical cord is rarely analyzed, except for umbilical artery blood flow patterns that are mainly used to further assess well-being of growth-restricted fetuses. At present time, it appears prudent to exercise more detailed umbilical cord analysis, including but not limited to vessel number, coiling patterns and cord thickness, during the fetal...

Prognostic significance of the interaction between abnormal umbilical and middle cerebral artery Doppler velocimetry in pregnancies complicated by fetal growth restriction

To evaluate the prognostic significance of the interaction between umbilical artery (UA) and middle cerebral artery (MCA) Doppler measurements in pregnancies complicated by fetal growth restriction (FGR). Cohort study. Third-level Perinatology Center in Northern Italy. A study of 184 singleton pregnancies at 24-35 weeks' gestational age complicated by FGR and abnormal UA Doppler measurements. FGR was diagnosed by serial ultrasonograms. Neonatal brain damage was defined as the presence of cystic leukomalacia or grade III-IV intraventricular hemorrhage. Perinatal death and neonatal brain damage. The prevalence of fetal/neonatal death or brain damage was 18.2% (16/88) in pregnancies with UA absent/reversed diastolic flow and 4.2% (4/96) in those with increased UA Doppler pulsatility. Stepwise logistic regression identified decreasing gestational age (OR=1.75, 95% confidence interval, CI=1.35-2.22) and absent/reversed UA blood flow (OR=3.34, 95% CI=1.1-10.9) as predictors of fetal/neonatal death or brain damage. A MCA pulsatility index below the 10th percentile was a risk factor for fetal/neonatal death or brain damage among women with absent/reversed UA diastolic flow (14/53 as compared to 2/35; OR=5.9, CI =1.4-40.3) but not in pregnancies with forward velocity (1/33 as compared to 3/63; OR=0.63, 95% CI=0.02-6.13, Synergy index=27.7, p=0.007). In pregnancies complicated by FGR and absent/reversed UA end diastolic flow, vasodilatation of the MCA is a risk factor for neonatal death or brain damage.

Small for gestational age preterm infants and relationship of abnormal umbilical artery Doppler blood flow to perinatal mortality and neurodevelopmental outcomes

To determine the outcomes of preterm small for gestational age (SGA) infants with abnormal umbilical artery (UA) Doppler studies. A retrospective cohort study of SGA singleton infants delivered between 24 and 32 weeks gestation at King Edward Memorial Hospital, Perth, who had UA Doppler studies performed within seven days of birth. Main outcomes assessed were perinatal mortality and morbidity, and neurodevelopmental outcomes at >or= 1 year of age. Outcomes were compared by normality of UA blood flow. There were 119 infants in the study: 49 (41%) had normal UA Doppler studies, 31 (26%) had an increased systolic-diastolic ratio >or= 95th centile, 19 (16%) had absent end diastolic blood flow (AEDF) and 20 (17%) had reversed end-diastolic flow (REDF). Infants in the AEDF and REDF groups were delivered significantly more preterm (P = 0.006) and had lower birthweights (P < 0.001). Ninety four per cent (110 of 117) of live born infants survived. Neurodevelopmental follow-up at 12 months of age or more (median 24 months) was available on 87 of 108 (81%) of live children. Twenty-eight per cent (11 of 39) of fetuses who had had AEDF or REDF died or were classified with moderate or severe disability. There was no significant association between abnormality of UA blood flow, perinatal morbidity, perinatal mortality and neurodevelopmental disability after correction for gestational age. Fetuses that are SGA with abnormal UA Doppler studies remain at significant risk of perinatal death, perinatal morbidity and long-term neurodevelopmental disability, associated with their increased risk of preterm birth.

A Modification of the Uterine Artery Restriction Technique in the Guinea Pig Fetus Produces Asymmetrical Ultrasound Growth

Aims To evaluate the use of diathermy ablation of branches of the uterine artery to produce growth restriction in the fetal guinea pig, and to compare this new approach with the more conventional use of uterine artery ligation. The development of growth restriction was documented by measuring fetal biparietal diameter (BPD) and the resistance index (RI) of the umbilical artery blood flow velocity waveform. Methods At 30–35 days of gestation (term = 70 days), one uterine artery was ligated in 29 sows. In another 16 sows, branches of one uterine artery were ablated using diathermy. Fetuses in contralateral horns were used as controls. Ultrasound measurements were made weekly, and at 59–69 days of gestation animals were euthanased to determine fetal position in utero as well as fetal and placental weights. In some fetuses, brain and liver weights were also recorded. Results Both surgical techniques resulted in similar reductions in fetal body and placental weights. The number of fetuses surviving to term was greater in the diathermy group (53%) compared to the ligation group (22%) ( P < 0.05). Results from these two groups were combined and referred to as “treated” fetuses. The brain/liver weight ratio was increased by 245% in the treated fetuses compared to control fetuses. Ultrasound measures of BPD in the treated fetuses were within the normal range. The mean RI of the treated group showed a slight but significant increase near term compared to the mean RI of the normal range. Conclusion We have shown that the diathermy technique produces asymmetrical fetal growth restriction (with normal head size) in the guinea pig to the same extent as the conventional ligation technique. It is associated with a lower fetal mortality rate and therefore should be the preferred method. The minimal increase in umbilical artery resistance index only at the end of gestation amongst the intrauterine growth restriction (IUGR) fetuses suggests that an obliterative vasculopathy in the umbilical circulation is not the cause of growth failure when there is maternal uteroplacental restriction.

829: Temporal changes in fetal heart rate patterns—a new dimension in fetal assessment

To compare temporal changes (trends) in computed FHR parameters obtained by numerical analysis of repeated non-stress tests between normal pregnancies and pregnancies with an abnormal biophysical profile or an increase in the resistance to flow in umbilical artery blood flow velocity waveforms (FVW's).

Correlation of placental pathology with prenatal ultrasound findings

There have been recent major advances in obstetric ultrasound, regarding both improved technologies and sonographer expertise, which have resulted in changes in antenatal obstetric management. The placenta is routinely examined...

Uterine activity: implications for the condition of the fetus

The aim of this review is to provide more insight in the fetal mechanisms as a response to uterine contractions and to emphasize the importance of correct assessment of uterine activity (UA) patterns during labor. UA causes a decreased flow through the uterine artery. In the healthy uncompromised fetus, this will not cause fetal acidemia. The fetus has developed certain protection mechanisms to survive labor; (1) During a contraction, fetal preload increases and enables the fetus to maintain a constant blood flow through the umbilical artery and (2) UA increases the blood flow in the fetal middle cerebral artery, i.e., a brain sparing effect. The shortcoming of those protection mechanisms in the compromised fetus and in case of excessive UA increases the risk of adverse fetal outcome. The brain sparing effect will become more pronounced to compensate for the decreased umbilical artery blood flow and fetal oxygen saturation. Maintenance of normal UA, especially a sufficiently long relaxation time, is essential so that the supply of well oxygenated maternal blood to the intervillous space will be restored and the fetal cerebral oxygen saturation can remain stable. Adequate UA monitoring is a prerequisite for proper reading and interpretation of cardiotocograms. It alarms in cases of excessive UA and can help to prevent fetal acidemia. Uterine contraction monitoring deserves full attention in daily obstetric practice.

Fetal ductus venosus, middle cerebral artery and umbilical artery flow responses to uterine contractions in growth‐restricted human pregnancies

To explore fetal ductus venosus (DV) flow velocity changes relative to umbilical artery (UA) blood flow and brain-sparing flow (BSF) during uterine contractions. Forty-five term fetuses suspected of having growth restriction were exposed to an oxytocin challenge test (OCT) with simultaneous Doppler velocimetry in the UA, middle cerebral artery (MCA) and DV. Basal BSF was defined as a MCA-to-UA pulsatility index (PI) ratio of < 1.08, and de novo BSF as a decrease in MCA-PI of > or = 1 SD (equivalent to a value of 0.24 units) during the OCT. Basal DV flow velocities were lower in the BSF group (n = 7) than they were in the non-BSF group (n = 38). During the OCT, DV flow velocity parameters changed in neither group but MCA-PI decreased in the non-BSF group. A crude de novo BSF was not associated with DV flow velocity changes, but when UA-PI changes were considered, a serial relationship was found between decreased UA-PI, increased DV flow velocity, and decreased MCA-PI. When UA-PI increased, the MCA-PI still decreased (though not significantly) but DV flow velocity parameters remained unchanged. Established fetal BSF is associated with low DV flow velocities, but in an acute sequence there might be two contrasting courses along which BSF develops: one with an increase and one with a decrease in the UA vascular flow resistance. In the former situation the DV flow velocity increases, while in the latter situation the role of the DV in the acute redistribution of fetal blood flow is unclear.

Einsatz von Nabelschnur-Doppler bei vorzeitiger Plazentalösung: zwei klinische Fallberichte

Hintergrund: Die dopplersonografische Untersuchung der A. umbilicalis ist eine etablierte Methode zur Überwachung von Hochrisikoschwangerschaften. Daten über dessen Einsatz in Akutsituationen, wie bei vorzeitiger Plazentalösung, sind allerdings rar und kontrovers. Fallberichte: Wir berichten von zwei Patientinnen, die in der 31 + 2 und 34 + 2 Schwangerschaftswoche (SSW) mit Status post vaginaler Blutung in unsere Klinik eingewiesen wurden. Bei der Aufnahme konnte keine Blutung festgestellt werden und sowohl klinisch als auch ultrasonografisch konnte kein Hinweis für eine Plazentalösung gefunden werden. Beide Patientinnen zeigten einen normalen Blutfluss (positiver enddiastolischer Fluss) in den Nabelschnurarterien bei pathologischem CTG. Eine zusätzliche Wachstumsrestriktion ergab bei einem Feten weitere Hinweise auf eine vorbestehende chronische fetale Asphyxie. In beiden Fällen wurden asphyktische Kinder mittels Kaiserschnitt entbunden. Die histologischen Endbefunde der Plazenten zeigten deutliche retroplazentare Hämatome und bestätigten die postpartale Diagnose der vorzeitigen Placentalösung. Schlussfolgerung: Die dopplersonografische Untersuchung der A. umbilicalis bei vorzeitiger Plazentalösung bringt keine zusätzliche Information zur Diagnoseerstellung bei Verdacht auf vorzeitige Plazentalösung. Sie kann darüber hinaus falsch unauffällige Befunde liefern.

P46.07: Perinatal outcome according to umbilical artery blood flow velocity waveform of term pregnancies with small for gestational age pregnancies

P46.07: Perinatal outcome according to umbilical artery blood flow velocity waveform of term pregnancies with small for gestational age pregnancies

Middle cerebral artery blood flow velocities and pulsatility index and the cerebroplacental pulsatility ratio: longitudinal reference ranges and terms for serial measurements

To establish reference ranges suitable for serial assessments of the fetal middle cerebral (MCA) and umbilical (UA) artery blood flow velocities, pulsatility index (PI) and cerebroplacental pulsatility ratio and to provide terms for calculating conditional reference intervals suitable for individual serial measurements. This was a longitudinal study of 161 singleton pregnancies. Using Doppler ultrasound, MCA and UA blood velocities and PI were determined three to five times at 3-5-week intervals over a gestational age range of 19-41 weeks. Polynomial regression lines for the 95th, 50th and 5th percentiles were calculated for the peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV), PI and cerebroplacental ratio. Terms for calculating conditional reference intervals were established. Based on 566 observations our new longitudinal reference ranges for fetal middle cerebral PSV, TAMXV and PI provided terms for calculating conditional reference intervals (i.e. predicting expected 95% confidence limits based on a previous measurement), and correspondingly for the cerebroplacental ratio (n = 550). The reference ranges were at some variance with those of previous cross-sectional studies. The narrow 95% confidence limits for the 5(th) and 95(th) percentiles ensured reliable ranges. We have established longitudinal reference ranges appropriate for the serial assessment of MCA blood velocities and PI and cerebroplacental ratio. Particularly the terms for calculating conditional ranges based on a previous observation make this system more appropriate for longitudinal monitoring than are cross-sectional data.

Application of high‐intensity focused ultrasound for umbilical artery occlusion in a rabbit model

To investigate the application of high-intensity focused ultrasound (HIFU) for fetal umbilical artery blood flow occlusion in a rabbit model. A prototype HIFU transducer in combination with an imaging probe with Doppler capability was constructed. Using this transducer, HIFU was applied at 1.4, 2.75 or 5.5 kW/cm(2) through the maternal abdominal skin to the fetal intra-abdominal umbilical arteries of four time-mated Japanese White rabbits (11 fetuses) on gestational day 25. Courses of 5-s HIFU exposure were performed until cessation of umbilical blood flow and cardiac arrest were confirmed by Doppler ultrasonography. Fetal necropsy was performed and exposed lesions were assessed by microscopic histological analysis. The mean diameter of the fetal umbilical artery was 0.6 +/- 0.2 mm and the mean peak systolic velocity of arterial blood flow was 44.7 +/- 18.5 cm/s. When HIFU was applied at 5.5 kW/cm(2), blood flow was completely occluded within 15 courses. HIFU exposure brought about vacuolar degeneration and destruction of elastic fibers in the tunica media of the artery. HIFU can be used to occlude umbilical artery blood flow in fetal rabbits.

REGULATION OF MURINE MATERNAL AND FETAL HEMODYNAMIC FUNCTION BY HEME OXYGENASE.

Heme oxygenase (HO) regulates vascular tone and blood pressure through the production of the vasodilator carbon monoxide (CO), derived from the heme degradation pathway. During pregnancy, the maternal circulation undergoes significant adaptations to accommodate for the hemodynamic demands of the developing fetus. Our objective was to investigate the role of HO and its bioactive product, CO, on maternal and fetal hemodynamics during pregnancy. In this study, we hypothesized that CO regulates maternal vascular tone, affecting uteroplacental artery dilation and placental perfusion and subsequently influencing fetal hemodynamic function. Compared with age-matched nonpregnant (control) levels, baseline total body CO excretion (VeCO) rates and blood carboxyhemoglobin (COHb) levels in pregnant mice were significantly elevated as well as HO activity in maternal livers, spleens, and placentas. Placental HO activity was the highest at embryonic ages E12.5 through E15.5. The maternal abdominal aorta (AA) was significantly dilated in pregnant mice compared with nonpregnant controls (0.88 vs 0.68 mm, respectively). To elucidate the function of HO and the production of CO during pregnancy, mice at ≈E12.5 to E14.5 were administered tin mesoporphyrin (SnMP), a potent HO inhibitor, at a dose of 30 μmol/kg, IV. Maternal heart rate and AA diameter, as well as fetal heart rate and umbilical artery blood flow and diameter, were measured using microultrasonography. Two hours post-SnMP administration, VeCO levels were reduced by 20%, and HO activity was significantly inhibited in maternal livers and placentas (80% and 90%, respectively) but only slightly (10%) in the fetal liver. In addition, AA was significantly constricted by 33% (0.88-0.59 mm); this effect was not observed in SnMP-treated nonpregnant mice. Furthermore, maternal heart and respiratory rates were elevated. Umbilical artery blood flow and fetal heart rate increased 44% and 38%, respectively, but umbilical artery diameter did not change. We conclude that during pregnancy, elevated levels of CO are produced by increases in HO activity in the maternal liver and placenta and play an important role in maintaining maternal vascular tone and fetal hemodynamic function. This work was study was supported in part by the Mary L. Johnson and Christopher Hess Research Funds.

Changes in Umbilical Arterial Blood Flow by an Intraamniotic Distilled Water Infusion

Changes in Umbilical Arterial Blood Flow by an Intraamniotic Distilled Water Infusion

Increased expression of N-myc downstream-regulated gene 1 (NDRG1) in placentas from pregnancies complicated by intrauterine growth restriction or preeclampsia

N-myc downstream-regulated gene 1 (NDRG1) modulates placental response to hypoxia. We therefore hypothesized that the expression of NDRG1 is altered in placentas from pregnancies complicated by intrauterine growth restriction (IUGR) or preeclampsia (PE), which are associated with fetoplacental underperfusion and cellular hypoxia. Thirty-five pregnant women in the third trimester of pregnancy were recruited according to the following 3 groups: (1) normal term pregnancy (n = 10), (2) pregnancy complicated by IUGR (n = 9), and (3) pregnancy with severe PE (n = 16). Placental samples were collected after cesarean delivery without labor. NDRG1 was measured with the use of immunostaining, Western blot, and real-time quantitative polymerase chain reaction (RT-qPCR). Umbilical artery blood flow velocity waveforms were recorded by Doppler ultrasound in women with IUGR and PE. By using immunostaining, we found a predominant expression of NDRG1 in the cytoplasm of villous trophoblasts. The expression of NDRG1 in samples from PE or IUGR was higher than control, with highest expression in PE. We confirmed these results by using immunoblotting and RT-qPCR. There was no correlation between the level of NDRG1 and umbilical artery blood flow. The expression of NDRG1 is upregulated in placentas from pregnancies complicated by severe PE or IUGR. This finding likely reflects trophoblast response to hypoxic injury.

414 COLOR DOPPLER EVALUATION OF UMBILICAL BLOOD FLOW DURING PREGNANCY IN COWS

There are few reports describing the use of Doppler for reproductive imaging in large animals; only one study (in mares) assessed umbilical blood flow (Bollwein et al. 2004 Theriogenology 61, 499–509). Conditions that constrict the placental vascular bed (i.e. hemorrhage, thrombosis, abnormal development, etc.) increase resistance to incoming blood. Thus, blood flow in umbilical arteries can be used to monitor placental development and function (Giles et al. 1985 Brit. J. Obstet. Gynaecol. 92, 31–38). The objective of the present study was to characterize the Doppler flow velocity waveform in umbilical arteries of cows with apparently normal pregnancies. Twenty-three multiparous, nonlactating Aberdeen Angus cows with pregnancies achieved after transfer of embryos derived by IVF (n = 10) or multiple ovulation and embryo transfer (MOET) (n = 13) were examined weekly from 5 to 38 weeks of gestation. Ultrasonography (Toshiba Nemio 20, Tokyo, Japan) was done using a 5–10 MHz intraoperative finger transducer (transrectal) from 5 to 17 weeks of pregnancy and thereafter using a 3–6 MHz linear-array transducer (transabdominal). The interrogation angle (between the ultrasound beam and the artery) ranged from 45° to 60°. Three resistance indices were calculated: A/B ratio, Resistance Index (RI) = (A − B)/A, and Pulsatility Index (PI) = (A − B)/M. [A = systole, B = diastole, and M = mean maximum Doppler-Shift frequency over the cardiac cycle.] The mean ± SEM duration of pregnancy was 285 ± 1.6 days (range: 269 to 291 days). A repeated measure ANOVA was used to detect differences between groups for every week using the Wald-Wolfowitz test (InfoStat V1.5, FCA, Universidad de Córdoba, Córdoba, Argentina). All 3 resistance indices decreased (by &amp;gt;50%) until 26 weeks, with no substantial change thereafter (Table 1). From 5 to 18 weeks of pregnancy, blood flow was characterized by a systolic pattern (i.e. high resistance with absence of diastolic flow); at 20 weeks, all fetuses had a diastolic flow, consistent with low resistance. There were differences (P &amp;lt; 0.05) between IVF- and MOET-derived pregnancies for RI and PI at 38 and 26 weeks of gestation, respectively, indicating differences in the placental vascular development at these weeks of gestation. In conclusion, umbilical cord blood flow in cattle was characterized by high resistance (5 weeks of gestation), but resistance decreased until 26 weeks; consequently, blood flow was initially systolic but became diastolic. Doppler sonography was useful for assessment of umbilical blood flow from 5 to 38 weeks of pregnancy, and may be useful for assessing placental function in pregnancies under risk, e.g. clone-derived pregnancies (Bertolini et al. 2002 Theriogenology 57, 181–187). Table 1. RI and PI at 19, 22, 26, 30, and 38 weeks of pregnancy in IVF- and MOET-derived pregnancies (mean ± sd)