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Z Geburtshilfe Neonatol 2002; 206(1): 1-8
DOI: 10.1055/s-2002-20943
Übersicht

© Georg Thieme Verlag Stuttgart · New York

Doppler-Sonographie des Ductus venosus: Messung, Evaluation und derzeitiger klinischer Stellenwert

Dopplersonography of the ductus venosus: assessment, evaluation and actual clinical importanceSt.  Ritter, H.  Jörn, W.  Rath
  • 1Frauenklinik für Gynäkologie und Geburtshilfe des Universitätsklinikums der Rheinisch-Westfälischen Technischen Hochschule (RWTH) Aachen
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Publication History

25. 1. 2001

9. 4. 2001

Publication Date:
08 March 2002 (online)

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Zusammenfassung

Der Ductus venosus (DV) verbindet die intraabdominale Umbilikalvene mit dem Infundibulum der V. cava inferior und entwickelt sich während der Schwangerschaft zu einem trompetenförmigen Gefäß mit einem isthmischen Eingang, durch welchen das Blut beschleunigt wird und via Foramen ovale direkt in den linken Vorhof gelangt, ohne sich mit sauerstoffarmem Blut vom rechten Vorhof zu vermischen. Am Tiermodell wird das Blutflussvolumen im DV und die dopplersonographisch aufgezeichnete Hüllkurve seiner Maximalgeschwindigkeiten maßgeblich durch den zentralen Venendruck und die Herzfrequenz gesteuert. Das dopplersonographisch ermittelte Flussgeschwindigkeitsprofil des DV ist zweigipflig: Der erste Gipfel repräsentiert die Maximalgeschwindigkeit während der ventrikulären Systole, der zweite die während der Diastole; die minimale Geschwindigkeit am Ende der Diastole und damit den Nadir der Hüllkurve markiert die Vorhofkontraktion. Die Bestimmung des Verhältnisses der Blutflussvolumina von DV zu Umbilikalvene spiegelt die Blutumverteilung wider, steigt bei hypoxämischen Ereignissen an und ist somit ein verlässlicherer Parameter für die Evaluierung von fetalem Distress als die ausschließliche Geschwindigkeitsmessung. Bei ausgeprägt retardierten Feten, Empfängerzwillingen bei FFTS (Feto-fetales Transfusionssyndrom) sowie tachyarrhythmieinduzierter Kardiomyopathie ist die Interpretation der Pulsatilität am DV ein geeignetes Verfahren zur fetalen Zustands- und Prognosebestimmung sowie zur Verlaufskontrolle; bei pathologischem Strömungsverhalten (Null- oder Negativfluss während der Vorhofkontraktion) ist in den meisten Fällen die vorzeitige Entbindung indiziert. Eine Senkung der perinatalen Morbidität und Mortalität konnte durch die Doppler-Messung des DV bisher nicht nachgewiesen werden. In der Frühschwangerschaft kann die Doppler-Flusskurvenanalyse am DV einerseits zur Detektion von Feten mit chromosomalen Aberrationen und andererseits zur Detektion von sowohl chromosomal euploiden als auch aneuploiden Feten mit Herzfehlern beitragen.

Abstract

The ductus venosus (DV) connects the intra-abdominal umbilical vein with the infundibulum of the IVC and develops during pregnancy to a trumpet-shaped structure with a narrow isthmus that accelerates the blood jet crossing the IVC directly to the left atrium via the foramen ovale avoiding mixing with deoxygenated blood from the right chamber. In animal studies, blood flow and dopplersonographically analyzed blood flow velocity waveforms mainly is controlled by heart rate and central venous pressure. The velocity waveform of the DV contains two peak components: the first indicates systolic velocity of the ventricle, the second peak diastolic velocity. A nadir is seen during atrial contraction. In animal studies, DV blood velocity in hypoxemia is influenced by central venous pressure and heart rate. The determination of the DV/UV ratio reflects the redistribution of blood flow, increases in hypoxemia and is therefore more reliable than blood velocity measurement for the detection and evaluation of fetal distress. In cases with severely growth-restricted fetuses, recipient twin in TTTS (twin-to-twin transfusion syndrome), tachyarrhythmia-induced cardiomyopathia and congenital heart disease, the measurement and interpretation of DV Doppler waveform pulsatility seems to be a useful tool that provides important information on the fetal condition and outcome. In cases of zero or reverse flow during atrial contraction in most cases the delivery of the fetus is indicated. An improvement of morbidity and mortality using Doppler sonography of the DV has not yet been proven. In cases of fetuses with or without chromosomal aberrations with major defects of the heart it can be used in addition to the standard screening methods of the first trimester of pregnancy for detection of heart failure.

Schlüsselwörter

Ductus venosus - fetale Doppler-Sonographie - Flusskurvenanalyse - Pränataldiagnostik

Key words

Ductus venosus - fetal Doppler - blood flow velocity waveform analysis - prenatal diagnosis

Literatur

  • 1 Acharya G, Kiserud T. Pulsations of the ductus venosus blood flow velocity and diameter are more pronounced at the outlet than at the inlet.  Eur J Obstet Gynecol Reprod Biol. 1999;  84 149-154
    CrossrefPubMedGoogle Scholar
  • 2 Adeagbo A SO, Breen C A, Cutz E, Lees J G, Olley P M, Coceani F. Lamb ductus venosus: evidence of a cytochrome P-450 mechanism in its contractile tension.  J Pharmacol Exp Ther. 1990;  252 875-879
    PubMedGoogle Scholar
  • 3 Adeagbo A SO, Bishai I, Olley P M, Coceani F. Evidence for a role of prostaglandine I2 and thromboxane A2 in the ductus venosus of the lamb.  Can J Physiol Pharmacol. 1984;  63 1101-1105
    PubMedGoogle Scholar
  • 4 Adeagbo A SO, Coceani F, Olley P M. The response of the lamb ductus venosus to prostaglandins and inhibitors of prostaglandin and thromboxane synthesis.  Circ Res. 1982;  51 580-586
    PubMedGoogle Scholar
  • 5 Bahlmann F, Wellek S, Reinhardt I, Merz E, Steiner E, Welter C. Reference values of ductus venosus flow velocities and calculated waveform indices.  Prenat Diagn. 2000;  20 623-634
    CrossrefPubMedGoogle Scholar
  • 6 Bellotti M, Pennati G, De Gasperi C, Battaglia F C, Ferrazzi E. Role of the ductus venosus in distribution of umbilical blood flow in human fetuses during second half of pregnancy.  Am J Physiol Heart Circ Physiol. 2000;  279 H1256-1263
    PubMedGoogle Scholar
  • 7 Borrell A, Antolin E, Costa D, Farre M T, Martinez J M, Fortuny A. Abnormal ductus venosus blood flow in trisomy 21 fetuses during early pregnancy.  Am J Obstet Gynecol. 1998;  179 1612-1617
    CrossrefPubMedGoogle Scholar
  • 8 Brezinka C, Hagenaars A M, Wladimiroff J W, Los F J. Fetal ductus venosus flow velocity waveforms and maternal serum AFP before and after first-trimester transabdominal chorionic villus sampling.  Prenat Diagn. 1995;  15 699-703
    PubMedGoogle Scholar
  • 9 Capponi A, Rizzo G, Rinaldo D, Arduini D, Romanini C. The effects of fetal blood sampling on ductus venosus velocity waveforms.  Ultrasound Obstet Gynecol. 1995;  5 241-246
    PubMedGoogle Scholar
  • 10 Chang C, Chang F, Yu C, Liang R, Ko H, Chen H. Systemic assessment of fetal hemodynamics by Doppler ultrasound.  Ultrasound Med Biol. 2000;  26(5) 777-785
    CrossrefPubMedGoogle Scholar
  • 11 Coceani F. The control of the ductus venosus: an update.  Eur J Ped. 1993;  152 967
    PubMedGoogle Scholar
  • 12 Coceani F, Olley P M. The control of cardiovascular shunts in the fetal and perinatal period.  Can J Pharmacol. 1988;  66 1129-1134
    PubMedGoogle Scholar
  • 13 Coceani F, Adeagbo A SO, Cutz E, Olley P M. Autonomic mechanisms in the ductus venosus of the lamb.  Am J Physiol. 1984;  247 H17-24
    PubMedGoogle Scholar
  • 14 DeVore G R, Horenstein J. Ductus venosus index: a method for evaluating right ventricular preload in the second-trimester fetus.  Ultrasound Obstet Gynecol. 1993;  3 338-342
    PubMedGoogle Scholar
  • 15 Edelstone D I. Regulation of blood flow through the ductus venosus.  J Dev Physiol. 1980;  2 219-238
    PubMedGoogle Scholar
  • 16 Edelstone D I, Rudolph A M, Heymann M A. Effects of hypoxemia and decreasing umbilical flow on liver and ductus venosus blood flows in fetal lambs.  Am J Physiol. 1980;  238 H656-663
    PubMedGoogle Scholar
  • 17 Edelstone D I, Rudolph A M, Heymann M A. Liver and ductus venosus blood flows in fetal lambs in utero.  Circ Res. 1978;  42 426-433
    PubMedGoogle Scholar
  • 18 Gembruch U, Krapp M, Germer U, Baumann P. Venous Doppler in the sonographic surveillance of fetuses with supraventricular tachycardia.  Eur J Obstet Gynecol. 1999;  84 187-192
    CrossrefPubMedGoogle Scholar
  • 19 Gembruch U, Baschat A A, Caliebe A, Gortner L. Prenatal diagnosis of ductus venosus agenesis: a report of two cases and review of the literature.  Ultrasound Obstet Gynecol. 1998;  11 185-189
    PubMedGoogle Scholar
  • 20 Gembruch U, Krapp M, Baumann P. Changes of venous blood flow velocity waveforms in fetuses with supraventricular tachycardia.  Ultrasound Obstet Gynecol. 1995;  5 394-399
    CrossrefPubMedGoogle Scholar
  • 21 Gest A L, Martin C G, Moise A A, Hansen T N. Reversal of venous blood flow with atrial tachycardia and hydrops in fetal sheep.  Pediatr Res. 1990;  28 223-226
    CrossrefPubMedGoogle Scholar
  • 22 Gudmundsson S. Importance of venous flow assessment for clinical decision-making.  Eur J Obstet Gynecol Reprod Biol. 1999;  84 173-183
    CrossrefPubMedGoogle Scholar
  • 23 Gudmundsson S, Tulzer G, Huhta J C, Marsal K. Venous Doppler in fetuses with absent end-diastolic flow in the umbilical artery.  Ultrasound Obstet Gynecol. 1996;  7 262-267
    CrossrefPubMedGoogle Scholar
  • 24 Gudmundsson S, Hökegard K H, Kjellmer I, Marsal K. Fetal lamb ductus venosus and umbilical venous blood velocity during hypoxia.  J Maternal Fetal Invest. 1993;  3 191-197
    PubMedGoogle Scholar
  • 25 Gudmundsson S, Huhta J C, Wood D, Tulzer G, Cohen A W, Weiner S. Venous Doppler ultrasonography in the fetus with nonimmune hydrops.  Am J Obstet Gynecol. 1991;  164 33-37
    PubMedGoogle Scholar
  • 26 Hecher K, Hackelöer B J. Cardiotocogramm compared to Doppler investigation of the fetal circulation in premature growth-retarded fetus: longitudinal observations.  Ultrasound Obstet Gynecol. 1997;  9 152-161
    PubMedGoogle Scholar
  • 27 Hecher K, Snijders R, Campbell S, Nicolaides K. Fetal venous, intracardiac, and arterial blood flow measurements in intrauterine growth retardation: relationship with fetal blood gases.  Am J Obstet Gynecol. 1995;  173 10-15
    CrossrefPubMedGoogle Scholar
  • 28 Hecher K, Snijders R, Campbell S, Nicolaides K. Fetal venous, arterial, and intracardiac blood flows in red blood cell isoimmunization.  Obstet Gynecol. 1995;  85 122-128
    CrossrefPubMedGoogle Scholar
  • 29 Hecher K, Ville Y, Snijders R, Nicolaides K. Doppler studies of the fetal circulation in twin-twin transfusion syndrome.  Ultrasound Obstet Gynecol. 1995;  5 318-324
    CrossrefPubMedGoogle Scholar
  • 30 Hecher K, Campbell S, Doyle P, Harrington K, Nicolaides K. Assessment of fetal compromise by Doppler ultrasound investigation of the fetal circulation. Arterial, intracardiac, and venous blood flow velocity studies.  Circulation. 1995;  91 129-138
    CrossrefPubMedGoogle Scholar
  • 31 Hecher K, Campbell S, Snijders R, Nicolaides K. Reference ranges for fetal venous and atrioventricular blood flow parameters.  Ultrasound Obstet Gynecol. 1994;  4 381-390
    CrossrefPubMedGoogle Scholar
  • 32 Hofstätter C, Plath H, Hannsmann M. Prenatal diagnosis of abnormalities of the fetal venous system.  Ultrasound Obstet Gynecol. 2000;  15 231-241
    Google Scholar
  • 33 Hofstätter C, Gudmunsson S, Dubiel M, Marsal K. Ductus venosus velocimetry in high-risk pregnancies.  Eur J Obstet Gynecol Reprod Biol. 1996;  70 135-140
    CrossrefPubMedGoogle Scholar
  • 34 Huisman T W, Brezinka C, Stewart P A, Stijnen T, Wladimiroff J W. Ductus venosus flow velocity waveforms in relation to fetal behavioural state.  Br J Obstet Gynaecol. 1994;  101 220-224
    PubMedGoogle Scholar
  • 35 Huisman T W, Stewart P A, Wladimiroff J W. Ductus venosus blood flow velocity waveforms in the human fetus - a Doppler study.  Ultrasound Med Biol. 1992;  18 33-37
    CrossrefPubMedGoogle Scholar
  • 36 Jensen A, Roman C, Rudolph A M. Effects of reduced uterine blood flow on fetal blood flow distribution and oxygen delivery.  J Dev Physiol. 1991;  15 309-323
    PubMedGoogle Scholar
  • 37 Kiserud T, Ozaki T, Nishina H, Rodeck C, Hanson M A. Effect of NO, phenylephrine, and hypoxemia on ductus venosus diameter in fetal sheep.  Am J Physiol Heart Circ Physiol. 2000;  279 H1166-H1171
    PubMedGoogle Scholar
  • 38 Kiserud T. Fetal venous circulation - an update on hemodynamics.  J Perinat Med. 2000;  28 90-96
    CrossrefPubMedGoogle Scholar
  • 39 Kiserud T, Hellevik L R, Hanson M A. Blood velocity profile in the ductus venosus inlei expressed by the mean/maximum velocity ratio.  Ultrasound Med Biol. 1998;  24 1301-1306
    CrossrefPubMedGoogle Scholar
  • 40 Kiserud T, Rasmussen S. How repeat measurements affect the mean diameter of the umbilical vein ductus venosus.  Ultrasound Obstet Gynecol. 1998;  11 419-425
    PubMedGoogle Scholar
  • 41 Kiserud T. In a different vein: the ductus venosus could yield much valuable information.  Ultrasound Obstet Gynecol. 1997;  9 369-372
    CrossrefPubMedGoogle Scholar
  • 42 Kiserud T, Stratford L, Hanson M A. Umbilical flow distribution to the liver and the ductus venosus: an in vitro investigation of the fluid dynamic mechanism in the fetal sheep.  Am J Obstet Gynecol. 1997;  177 86-90
    PubMedGoogle Scholar
  • 43 Kiserud T, Eik-Nes S H, Blaas H G, Gellevik L R, Simensen B. Ductus venosus blood velocity and the umbilical circulation in the seriously growth retarded fetus.  Ultrasound Obstet Gynecol. 1994;  4 109-114
    PubMedGoogle Scholar
  • 44 Kiserud T, Eik-Nes S H, Hellevik L R, Blaas H G. Ductus venosus blood velocity changes in cardiac diseases.  J Matern Fetal Invest. 1993;  3 15-20
    PubMedGoogle Scholar
  • 45 Kiserud T, Eik-Nes S H, Blaas H G, Hellevik L R. Foramen ovale: an ultrasonographic study of its relation to the inferior vena cava ductus venosus and hepatic veins.  Ultrasound Obstet Gynecol. 1992;  2 389-396
    PubMedGoogle Scholar
  • 46 Kiserud T, Eik-Nes S H, Blaas H G, Hellevik L R. Ultrasonographic velocimetry of the fetal ductus venosus.  Lancet. 1991;  338 1412-1414
    CrossrefPubMedGoogle Scholar
  • 47 Krapp M, Gembruch U, Baumann P. Venous blood flow pattern suggesting tachycardia-induced cardiomyopathy in the fetus.  Ultrasound Obstet Gynecol. 1997;  10 32-40
    CrossrefPubMedGoogle Scholar
  • 48 Loberant N, Herskovits M, Barak M, Ben-Elisha M, Herschkowitz S, Sela S, Roguin N. Closure of the ductus venosus in premature infants: findings on real-time gray-scale, color-flow doppler, and duplex sonography.  Am J Roentgenol. 1999;  172 227-229
    PubMedGoogle Scholar
  • 49 Loberant N, Barak M, Gaitini D, Herskovits M, Ben-Elisa M, Rougin N. Closure of the ductus venosus in neonates: Findings on real-time gray-scale, color flow Doppler, and duplex Doppler sonography.  Am J Roentgenol. 1992;  159 1083-1085
    CrossrefPubMedGoogle Scholar
  • 50 Mari G, Uerpairojkit B, Copel J A. Abdominal venous system in the normal fetus.  Obstet Gynecol. 1995;  86 729-733
    CrossrefPubMedGoogle Scholar
  • 51 Matias A, Montenegro N, Areias J C, Leite L P. Hemodynamic evaluation of the first trimester fetus with special emphasis on the venous return.  Hum Reprod Update. 2000;  6 177-189
    CrossrefPubMedGoogle Scholar
  • 52 Matias A, Huggon I, Areias J C, Montenegro N, Nicolaides K H. Cardiac defects in chromosomally normal fetuses with abnormal ductus venosus blood flow at 10 - 14 weeks.  Ultrasound Obstet Gynecol. 1999;  14 307-310
    CrossrefPubMedGoogle Scholar
  • 53 Matias A, Gomes C, Flack N, Montenegro N, Nicolaides K H. Screening for chromosomal abnormalities at 10 - 14 weeks: the role of ductus venosus blood flow.  Ultrasound Obstet Gynecol. 1998;  12 380-384
    CrossrefPubMedGoogle Scholar
  • 54 Meyer W W, Lind J. The ductus venosus and the mechanism of its closure.  Arch Dis Childh. 1966;  41 597-605
    PubMedGoogle Scholar
  • 55 Montenegro N, Matias A, Areias J C, Barros H. Ductus venosus revisited: a Doppler flow evaluation in the first trimester of pregnancy.  Ultrasound Med Biol. 1997;  23 171-176
    CrossrefPubMedGoogle Scholar
  • 56 Morin F CI. Prostaglandin E1 opens the ductus venosus in the newborn lamb.  Pediatr Res. 1987;  21 225-228
    PubMedGoogle Scholar
  • 57 Nakata M. Doppler velocity waveforms in ductus venosus in normal and small-for-gestational-age fetuses.  J Obstet Gynaecol Res. 1996;  22 489-496
    PubMedGoogle Scholar
  • 58 Oepkes D, Vandenbussche F P, Van Bel F, Kanhai H HH. Fetal ductus venosus blood flow velocities before and after transfusion in red-cell alloimmunized pregnancies.  Obstet Gynecol. 1993;  82 237-241
    PubMedGoogle Scholar
  • 59 Ozcan T, Sbracia M, d'Àncona R L, Copel J A, Mari G. Arterial and venous Doppler velocimetry in the severely growth-restricted fetus and associations with adverse perinatal outcome.  Ultrasound Obstet Gynecol. 1998;  12 39-44
    PubMedGoogle Scholar
  • 60 Paulick R P, Meyers R L, Rudolph C D, Rudolph A M. Venous and hepatic vascular responses to indomethacin and prostaglandin E1 in the fetal lamb.  Am J Obstet Gynecol. 1990;  163 1357-1363
    PubMedGoogle Scholar
  • 61 Pennati G, Bellotti M, Ferrazzi E, Bozzo M, Pardi G, Fumero R. Bloodflow through the ductus venosus in human fetus: calculation using Doppler velocimetry and computational findings.  Ultrasound Med Biol. 1998;  24 477-487
    CrossrefPubMedGoogle Scholar
  • 62 Rizzo G, Capponi A, Talone P E, Arduini D, Romanini C. Doppler indices from inferior vena cava and ductus venosus in predicting pH and oxygen tension in umbilical blood at cordocentesis in growth-retarded fetuses.  Ultrasound Obstet Gynecol. 1996;  7 401-410
    CrossrefPubMedGoogle Scholar
  • 63 Rudolph A M. Hepatic and ductus venosus blood flows during fetal life.  Hepatology. 1983;  3 254-258
    PubMedGoogle Scholar
  • 64 Rudolph A M. Distribution and regulation of blood flow in the fetal neonatal lambs.  Am J Physiol. 1980;  238 H656-663
    PubMedGoogle Scholar
  • 65 Rudolph C D, Meyer R L, Paulick R P, Rudolph A M. Effects of ductus venosus obstruction on liver and regional blood flows in the fetal lamb.  Pediatr Res. 1991;  29 347-352
    PubMedGoogle Scholar
  • 66 Schmidt K G, Silverman N H, Rudolph A M. Assessment of flow events at the ductus venosus-inferior vena cava junction and at the foramen ovale in fetal sheep by use of multimodal ultrasound.  Circulation. 1996;  93 826-833
    CrossrefPubMedGoogle Scholar
  • 67 Selam B, Koksal R, Oczan T. Fetal arterial and venous Doppler parameters in the interpretation of oligohydramnios in postterm pregnancies.  Ultrasound Obstet Gynecol. 2000;  15 403-406
    PubMedGoogle Scholar
  • 68 Senat M V, Schwärzler P, Alcais A, Ville Y. Longitudinal changes in the ductus venosus, cerebral transverse sinus and cardiotocogramm in fetal growth restriction.  Ultrasound Obstet Gynecol. 2000;  16 19-24
    CrossrefPubMedGoogle Scholar
  • 69 Sherer D M, Fromberg R A, Divon M Y. Prenatal ultrasonographic assessment of the ductus venosus: a review.  Obstet Gynecol. 1996;  88 626-632
    CrossrefPubMedGoogle Scholar
  • 70 van Splunder P, Stijnen T, Wladimiroff J W. Fetal atrioventricular, venous, and arterial flow velocity waveforms in the small-for-gestational age fetus.  Pediatr Res. 1997;  42 765-775
    PubMedGoogle Scholar
  • 71 van Splunder P, Stijnen T, Wladimiroff J W. Fetal pressure gradient estimations across the ductus venosus in early pregnancies using Doppler sonography.  Ultrasound Obstet Gynecol. 1995;  6 334-339
    PubMedGoogle Scholar
  • 72 Tchirikov M, Eisermann K, Rybakowski C, Schröder H J. Doppler ultrasound evaluation of ductus venosus blood flow during acute hypoxemia in fetal lambs.  Ultrasound Obstet Gynecol. 1998;  11 426-431
    PubMedGoogle Scholar
  • 73 Tchirikov M, Rybakowski C, Hüneke B, Schröder H J. Blood flow through the ductus venosus in singleton and multifetal pregnancies and in fetuses with intrauterine growth retardation.  Am J Obstet Gynecol. 1998;  178 943-949
    PubMedGoogle Scholar
  • 74 Weiner Z, Itskovitz-Eldor J. Hepatic distribution of the umbilical venous return in normal pregnancies.  J Matern Fetal Invest. 1995;  5 190
    PubMedGoogle Scholar
  • 75 Zickulnig L, Hecher K, Bregenzer T, Baz E, Hackelöer B J. Prognostic factors in severe twin-twin transfusion treated by endoscopic laser surgery.  Ultrasound Obstet Gynecol. 1999;  14 380-387
    PubMedGoogle Scholar
  • 76 Baschat A A, Gembruch U, Reiss I, Gortner L, Weiner C P, Harman C R. Relationship between arterial and venous Doppler and perinatal outcome in fetal growth restriction.  Ultrasound Obstet Gynecol. 2000;  16 407-413
    CrossrefPubMedGoogle Scholar
  • 77 Baschat A A, Gembruch U, Gortner L, Reiss I, Weiner C P, Harman C R. Coronary artery blood flow visualization signifies hemodynamic deterioration in growth-restricted fetuses.  Ultrasound Obstet Gynecol. 2000;  16 425-431
    PubMedGoogle Scholar
  • 78 Mäkikallio K, Vuolteenaho O, Jouppila P, Räsänen J. Association of severe placental insuffiency and systemic venous pressure rise in the fetus with increased neonatal cardiac troponin t levels.  Am J Obstet Gynecol. 2000;  183 726-731
    CrossrefPubMedGoogle Scholar
  • 79 Kurjak A. Are color and pulsed Doppler sonography safe in early pregnancy?.  J Perinat Med. 1999;  27 423-430
    CrossrefPubMedGoogle Scholar
  • 80 Rott H D. Clinical safety statement for diagnostic ultrasound.  Eur J Ultrasound. 1998;  8 67-68
    CrossrefPubMedGoogle Scholar

Dr. med. Stefan Ritter

Frauenklinik für Gynäkologie und Geburtshilfe

des Universitätsklinikums der RWTH Aachen

Pauwelsstraße 30

52074 Aachen

Email: s.ritter@post.rwth-aachen.de

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