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N Montenegro

Publications and source records attributed to N Montenegro.

36 records · Page 2Linked to original sources
PubMed1997

Ductus venosus revisited: a Doppler blood flow evaluation in the first trimester of pregnancy.

The functional role of the fetal ductus venosus (DV) is still poorly established. Few reports are available in the literature concerning assessment of fetal venous return during the late first trimester of pregnancy. Our objective was to determine the normal Doppler blood velocity waveform in the human fetal DV as early as 10-13 weeks gestation. Adopting strict methodological concerns, 61 Doppler blood flow evaluations of the DV considered technically acceptable were selected. Using transvaginal Doppler ultrasound, several DV haemodynamic parameters were assessed: peak systolic and diastolic velocities, time-averaged velocity, maximum velocity during atrial contraction, pulsatility index and fetal heart rate (FHR). Except for the FHR, no significant variations were observed for the above mentioned parameters during this period, and no correlation could be established between FHR and the different flow velocity parameters. Further knowledge about DV haemodynamics in the early phases of pregnancy may make a valuable contribution to the understanding of fetal venus return to the heart and cardiac function.

Blood Flow Velocity↗
PubMed1997

Increased fetal nuchal translucency: possible involvement of early cardiac failure.

The ultrasonographic measurement of nuchal translucency thickness at 10-13 weeks of gestation is accepted as an efficient method of screening for chromosomal abnormalities. However, the underlying mechanism producing increased nuchal translucency thickness is still poorly understood. The purpose of this study was to investigate the possible contribution of impaired cardiac function to such an increase, by studying the venous return in the ductus venosus, using Doppler ultrasound. In a total of 65 fetuses, nuchal translucency thickness was measured at 10-13 weeks of gestation by means of a transvaginal probe. Color-coded and pulsed Doppler ultrasound were also used to evaluate different hemodynamic parameters in the ductus venosus: maximum systolic and diastolic velocities, pulsatility index, lowest forward velocity during atrial contraction and fetal heart rate. Fetal nuchal translucency thickness of > or = 3 mm was found in 17 cases; in five of them there were chromosomal anomalies: four trisomy 21 and one trisomy 18. Of interest is the finding that in the five chromosomally abnormal fetuses with increased nuchal translucency thickness, the forward velocity during atrial contraction was consistently less than 2 cm/s (p < 0.001). This impairment of atrial contraction may well implicate cardiac failure and/or heart defects in the pathogenesis of increased nuchal translucency thickness in the first trimester of pregnancy. Furthermore, nuchal translucency may prove to be a sensitive marker for the early identification of fetal cardiac anomalies.

Blood Flow Velocity↗
PubMed1996

Fetal heart rate in trisomy 21 and other chromosomal abnormalities at 10-14 weeks of gestation.

Fetal heart rate was measured routinely as part of a prospective study examining the efficacy of screening for trisomy 21 by fetal nuchal translucency thickness and maternal age. In 6903 normal singleton pregnancies the fetal heart rate decreased from a mean of 171 bpm at 10 weeks of gestation to 156 bpm at 14 weeks (r = 0.413, p < 0.0001). In 85 trisomy 21 pregnancies, the mean heart rate was significantly higher than in the normal group (mean difference 0.67 SD, 95% confidence interval 0.42-0.92, t = 5.3, p < 0.001). The fetal heart rate in trisomy 18 and triploid fetuses was significantly lower and in trisomy 13 and Turner syndrome was higher than normal. There was no significant association between delta fetal heart rate and delta nuchal translucency thickness in either the normal (r = -0.018) or the trisomy 21 (r = -0.031) pregnancies. Consequently, the risk for chromosomal defects can be derived by combining data from maternal age, fetal nuchal translucency and fetal heart rate. The effectiveness of screening by this method was examined in a self-selected population with completed pregnancies that had undergone first-trimester scanning. This population contained 6903 normal and 29 trisomy 21 fetuses. For a false-positive rate of about 5%, the sensitivity for trisomy 21 was 48% by maternal age, 26% by fetal heart rate, 72% by nuchal translucency thickness, 59% by maternal age and fetal heart rate, 76% by maternal age and nuchal translucency thickness and 83% by a combination of maternal age, nuchal translucency thickness and fetal heart rate.

Chromosome Aberrations↗
PubMed1995

Reverse end-diastolic umbilical artery blood flow at 11 weeks' gestation.

This report describes a case of reverse end-diastolic blood flow in the umbilical artery of one of the fetuses of a twin pregnancy at 11 weeks' gestation. Cytogenetic studies after amniocentesis performed at 12 weeks revealed a 45.X karyotype of this twin whose death was registered 1 week later. Spontaneous delivery of the co-twin occurred at 37 weeks; the newborn was healthy and normal. This is the earliest record of reverse diastolic flow in the umbilical artery. Even in the first trimester of pregnancy this is an ominous sign and fatal demise is expected.

Adult↗
PubMed1994

Clinical significance of absent or reversed end diastolic velocity waveforms in umbilical artery.

Doppler ultrasound provides a non invasive method to assess fetal haemodynamics. We looked at the outcome of doppler velocimetry of the umbilical artery in three groups of pregnancies: those with positive end diastolic velocities (PED; n = 214), absent end diastolic velocities (AED; n = 178) and reversed end diastolic velocities (RED; n = 67). We collected our data from 9 European centers. Logistic regression showed that compared with pregnancies with hypertension only, pregnancies complicated by intra uterine growth retardation (IUGR) had a higher risk of developing absent or reversed end diastolic velocity waveforms (ARED) flow. ARED flow in the umbilical artery (odds ratio: OR = 3.1). Pregnancies complicated by both IUGR and hypertension had an even higher risk (OR = 7.4). Maternal age and smoking habits did not influence the risk of developing ARED flow. The overall perinatal mortality rate was 28%. Significantly more neonates in the ARED flow group needed admittance to the neonatal intensive care unit (PED group 60%, AED group 96%, RED group 98%). The OR for perinatal mortality in pregnancies complicated by AED flow was 4.0 and in RED flow was 10.6, compared with PED flow, even after adjustment for menstrual age. ARED flow in the umbilical artery did not influence the risk of respiratory distress syndrome or necrotising enterocolitis of the neonate, but ARED flow significantly influenced the risk of cerebral haemorrhage, anaemia, or hypoglycaemia. We advise that pregnancies complicated by IUGR and/or hypertension should be followed up with doppler velocimetry to trace utero-placental problems as early as possible. A caesarean section is recommended in all pregnancies complicated by ARED flow if the gestational age and predicted neonatal weight can be handled by the local neonatal intensive care unit.

Adult↗
PubMed1993

[Transvaginal endosonography and Doppler study in embryo-fetal hemodynamic assessment in the first pregnancy trimester].

Transvaginal endosonography is now currently used in obstetrics and gynecology practice and seems a promising tool for essential studies on first trimester pregnancy. High-resolution and duplex/color Doppler in vaginal probes have brought to light new chances for early investigations on embryonic-fetal haemodynamics. We report our experience in this field, together with a review of the literature, giving an overview on embryonic-fetal cardiovascular haemodynamics studied by this approach. Blood flow patterns of intracardiac flows as extra-cardiac circulation during first trimester pregnancy are reported.

Embryo, Mammalian↗
PubMedDate not supplied

Haemodynamic evaluation of the first trimester fetus with special emphasis on venous return.

Knowledge of the fetal circulation is a prerequisite for understanding the physiological behaviour of the developing fetus. In this overview dealing with Colour and Power Doppler ultrasound findings in the first trimester of pregnancy and its pathophysiological background, we aim to report on the methodological aspects, normal blood flow waveform patterns, normal reference values for haemodynamic parameters and potential clinical applications for both arterial and venous flow information (umbilical artery, descending aorta, middle cerebral artery, umbilical vein, inferior vena cava, ductus venosus) and atrioventricular valves. Particular emphasis is devoted to the venous return to the heart. Alterations in venous waveforms, particularly in the ductus venosus, are correlated with the pathophysiology of some fetal diseases and are suggested as a promising tool for the screening of cardiac impairment and as an alternative method for fetal biophysical surveillance.

Arteries↗
PubMedDate not supplied

Early antenatal diagnosis of cardiac defects using transvaginal Doppler ultrasound: new perspectives?

OBJECTIVE: Cardiac defects are the most prevalent congenital anomalies. Screening policies have adopted an 18- to 22-week ultrasound scan to detect such anomalies. However, diagnosis may be feasible early in pregnancy using transvaginal Doppler ultrasound. METHODS: Transvaginal ultrasound, including nuchal translucency (NT) measurement, is routinely performed at 10-13 weeks of gestation at our department. Complementary arterial and venous blood flow Doppler evaluation is also performed in cases of increased NT as a part of an ongoing research project. RESULTS: Ultrasound revealed complete atrioventricular septal defects in 2 trisomic fetuses (trisomy 18 and 21) at 12 and 13 weeks of gestation, respectively, with increased NT and abnormal venous blood flow velocity. CONCLUSIONS: Increased NT has been associated with major chromosomal anomalies and is being increasingly related to cardiac defects. Considering that venous blood flow patterns may provide additional clues to the cardiac function, it may be useful as a complementary tool for the earlier diagnosis of structural cardiac anomalies.

Adult↗
PubMedDate not supplied

[Pattern of intrauterine growth and Doppler flowmetry].

The aim of this study was to evaluate the accuracy of ultrasound biometric and hemodynamic fetal parameters for the prenatal diagnosis of intrauterine retardation in a sample of 438 pregnant women who had their first visit before the 16th week of gestation at the outpatient clinic of the Department of Obstetrics and Gynecology, S. Joào Hospital. The results are presented for 427 mother-infant pairs corresponding to singleton pregnancies uncomplicated by congenital malformations. The prevalence of SGA was 4.9%, 86.2% for AGA and 8.9% for LGA. A relatively low sensitivity and high specificity were calculated for the ultrasound parameters evaluated, as observed in previous studies performed in other populations. Mean values for the differences of umbilical vessels resistance index measured at 28-32 and 35-37 gestation weeks were significantly lower in SGA newborns, probably reflecting a sustained compromise of vascular compliance (umbilical/placental). The observed lack of agreement between the pre and the postnatal diagnosis of SGA emphasises the need to define local reference birthweight curves or the careful adoption of European standards obtained in populations identical to our.

Adult↗