Der Kaiserschnitt

[J9126]

Den ganzen Geburts-Hokuspokus müssen wir auch mal thematisieren. Wer ist dazu bewandert genug?

Da sollten wir mal 40Fieber oder den Kinderarzt ansprechen, auf Kidmed gabs dazu vor Jahren schonmal Erlebnisberichte der besonderen Art, bei denen Hausgeburten und Geburtshäuser ...sagen wir mal... nicht so gut weggekommen sind. So mit toten und geistig behinderten Kindern, die aber schön natürlich geboren worden sind.

[heterodyne]

Erlebnisberichte sind zwar für die Betroffenen tragisch, sagen aber auch nichts allgemeingültiges aus. Genausowenig wie die begeisterten Erlebnisberichte von Geburthäusern. Erlebnisberichte in jede Richtung finde ich problemlos überall, die werden mir sogar aufgedrängt.
Was schwieriger zu bekommen ist sind Fakten - so wie zB aus dem BMJ Artikel über Sterblichkeit
Noch ein Aspekt: was ist jetzt mit Ultraschall? Von kochendem Fruchtwasser über Lautstärke eines einfahrenden Zuges bekommt man auch hier einiges serviert. Seriöse Stellungnahmen konnte ich nicht finden. Nur Panikmache von Hebammenmund zu Hebammenohr, bzw werdende-Mutterohr. Man verzeihe mir dieses Schlechtmachen der Hebammen, zu viele von ihnen schwimmen einfach auf unseriösem Getue mit als daß ich diesen Berufsstand noch mit dem eigentlich gebührenden Respekt sehen könnte.

[Federvieh]

Das mit dem Ultraschall habe ich ebenfalls bereits gehört.

[Conni]

Das mit dem Ultraschall habe ich ebenfalls bereits gehört.

Und deswegen werden Vorsorgeuntersuchungen abgelehnt. Einfach irre.

[heterodyne]

Finde ich auch 

Allerdings habe ich kein Gegenargument außer daß jede Menge Föten friedlich unter Beschallung weiterschlafen bz sich weiter mit den Zehen spielen und dass Ultraschall für einen Menschen nicht zu hören ist, egal wie laut (zB Fledermaus).
Ich kann nur von meiner Erfahrung ausgehen und nicht zB belegen, dass der US im Wasser nicht hörbar wird (sorry, mein Physikunterricht ist einfach zu lange her und Selbstexperiment kann ich mangels Möglichkeiten nicht machen. Ich kann mir nicht vorstellen, dass das passiert, schliesslich müsste der Schall ja dann den Frequenzbereich wechseln) oder aber zB ein Fötus in einem anderen Frequenzbereich hört als ein Baby (ist zwar mMn sehr unwahrscheinlich, aber ich finde nix dazu)

[Federvieh]

Prenat Diagn. 2009 Dec;29(13):1204-12.
The safety of obstetrical ultrasound: a review.

Houston LE, Odibo AO, Macones GA.

Department of Obstetrics and Gynecology, Washington University in St. Louis, St. Louis, MO 63110, USA. houstonl@wudosis.wustl.edu
Abstract

Ultrasound is a commonly employed imaging modality in obstetrics and is generally regarded as safe to the fetus. Current ultrasound technology, however, has significantly higher output potential than older machines used in most clinical studies, and the safety profile for the increasing use of Doppler, 3-dimensional (D) and 4-D ultrasound with modern machines is unknown. This article reviews the current status of ultrasound safety within obstetrics, including proposed mechanisms of harm, existing scientific and clinical evidence regarding those mechanisms, and considerations of safety for the clinical user.
Copyright (c) 2009 John Wiley & Sons, Ltd.

PMID: 19899071 [PubMed - indexed for MEDLINE]

Publication Types, MeSH Terms
Publication Types:

   * Review

MeSH Terms:

   * Animals
   * Clinical Trials as Topic
   * Female
   * Hot Temperature/adverse effects
   * Humans
   * Pregnancy
   * Stress, Mechanical
   * Ultrasonography, Doppler/adverse effects
   * Ultrasonography, Prenatal/adverse effects*
   * Ultrasonography, Prenatal/standards

LinkOut - more resources

Hat da jemand zugriff? Found it (s. att.)

[Federvieh]

Obstet Gynecol. 1988 Apr;71(4):513-7.
The relationship of birth weight and intrauterine diagnostic ultrasound exposure.

Moore RM Jr, Diamond EL, Cavalieri RL.

Center for Devices and Radiological Health, Food and Drug Administration, Rockville, Maryland.
Abstract

Imaging with ultrasound is common in obstetric practice. Several laboratory animal studies have shown retardation in fetal growth after experimental ultrasound exposure. This investigation was conducted to determine whether human fetuses exposed to diagnostic ultrasound (sonography) have a greater risk of growth retardation than fetuses not so exposed. This retrospective cohort study compares the birth weights of 1598 exposed and 944 unexposed single live births at the Johns Hopkins Hospital in Baltimore, Maryland during calendar year 1981. Confounding variables, defined as those associated with both exposure status and birth weight outcome, were included in multivariable analysis. Both exposure to more than one ultrasound procedure and first exposure during the third trimester were associated with a reduction in birth weight. However, the most consistent effect associated with birth weight appeared to be the indication for an ultrasound examination. The relationship of ultrasound exposure and reduced birth weight appeared to be due to shared common risk factors, which lead to both exposure and a reduction in birth weight.

PMID: 3281071 [PubMed - indexed for MEDLINE]

[cohen]

Exkurs:
Das mit dem Kaiserschnitt ist noch viel schlimmer!!!!

Nach homöopathischem Gedankenmuster, werden die meisten Kinder welche per Sectio auf die Welt kommen, vom psorischen ins syphilitische Miasma "gedrückt" und somit viel anfälliger auf die erwähnten und diverse andere Krankheiten.

Beschädigtes Erbgut wegen Kaiserschnitt mit Homöopathie behandeln?

[Federvieh]

Obstet Gynecol. 2008 Jul;112(1):145-57.
Prenatal imaging: ultrasonography and magnetic resonance imaging.

Reddy UM, Filly RA, Copel JA; Pregnancy and Perinatology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Department of Health and Human Services, NIH.

Pregnancy and Perinatology Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Department of Health and Human Services, NIH, Bethesda, MD 20892-7510, USA. reddyu@mail.nih.gov
Abstract

The Eunice Kennedy Shriver National Institute of Child Health and Human Development held a workshop on September 18-19, 2006, to summarize the available evidence on the role and performance of current fetal imaging technology and to establish a research agenda. Ultrasonography is the imaging modality of choice for pregnancy evaluation due to its relatively low cost, real-time capability, safety, and operator comfort and experience. First-trimester ultrasonography extends the available window for fetal observation and raises the possibility of performing an early anatomic survey. Three-dimensional ultrasonography has the potential to expand the clinical application of ultrasonography by permitting local acquisition of volumes and remote review and interpretation at specialized centers. New advances allow performance of fetal magnetic resonance imaging (MRI) without maternal or fetal sedation, with improved characterization and prediction of prognosis of certain fetal central nervous system anomalies such as ventriculomegaly when compared with ultrasonography. Fewer data exist on the usefulness of fetal MRI for non-central nervous system anomalies.

PMID: 18591320 [PubMed - indexed for MEDLINE]PMCID: PMC2788813Free PMC Article

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2788813/?tool=pubmed

ULTRASOUND SAFETY
Ultrasound has a demonstrated record of safety for more than 50 years of clinical use. Although no independently replicated epidemiologic data exist to suggest harmful effects of ultrasonography in the fetus, ultrasonography is a form of energy with two main bioeffects in tissue: heat, a direct effect, and oscillatory movements, secondary to the alternating positive and negative pressure waves. These effects are inherent in the physical properties of ultrasonography and have not been shown to be harmful in humans.30 However, most safety data are epidemiologic, collected before the permissible output of scanners was increased by a factor of almost 8, around 1992.31 The U.S. Food and Drug Administration recommends against the use of medically unindicated or commercial prenatal ultrasonography.32
Although there is no evidence of harm, ultrasound power levels have gone up, and there is increasing use of more powerful color and spectral Doppler in the first trimester, so safety cannot be presumed. Dose is a quantitative measure that combines intensity and exposure time. No standard dose quantity has been identified for ultrasonography. Variation in tissue properties between individuals and scanning conditions influence dose in unpredictable ways. For all practical purposes, fetal dose cannot be precisely quantified. Documentation of dwell time, type of machine, and transducer used would begin to address the problem of lack of a dose metric for ultrasonography.
The bioeffects of clinical ultrasound exams are approximated by the thermal index for heating and by the mechanical index for cavitation effects. Both are indices of exposure, but neither takes time into account. Thermal index predicts potential for temperature increase, not actual rise, and it remains unknown whether there is a threshold for temperature-related bioeffects. Mechanical index expresses potential to induce inertial cavitation. Mechanical effects are less likely in the fetus, because foci susceptible to cavitation (ie, containing gas) are not present.30 Maternal body size is important because examinations may be prolonged in heavier women, whereas at the same time fetal exposure may be reduced per unit time due to attenuation of the acoustic beam at greater depths.
Evidence in animals shows that exposure to diagnostic ultrasonography can produce significant temperature increases in the fetal brain near bone. The critical questions include whether the extent of ultrasound-induced temperature rise is sufficient to create a hazard and whether there is a threshold for hyperthermia-induced birth defects. In addition, the determination of possible neurophysiologic effects or responses to clinically relevant exposures is needed. In a review of epidemiologic studies of human exposure to ultrasonography, there were no effects noted on childhood cancer, dyslexia, speech development, or congenital anomalies.33 However, there is very limited evidence that the frequent exposure of the human fetus to ultrasound waves may be associated with a nonsignificant decrease in newborn body weight,34 a reduction in the frequency of right-handedness,35 and delayed speech.36
Ang et al37 examined the effect of ultrasound waves on neuronal position within the embryonic cerebral cortex in mice. When mice were exposed to ultrasound waves for a total of 30 minutes or longer during neuronal migration, a small but statistically significant number of neurons failed to acquire their proper position and remained scattered within inappropriate cortical layers and/or in the subjacent white matter. The magnitude of dispersion of labeled neurons systematically increased with duration of exposure to ultrasound waves. The relevance of these findings for cortical development in humans is unclear. The ultrasound beam characteristics used in this study were well within clinical norms for fetal exams. There are, however, significant differences in the number of neurons and the size of the cerebral cortex between mouse and human. The distance between the exposed cells and transducer in Ang's experiments was shorter than in humans. Furthermore, the duration of neuronal production and the migratory phase of cortical neurons last 18 times longer in the human fetus than in mice. Thus, an exposure of 30 minutes represents a much smaller proportion of the time dedicated to development of the cerebral cortex in humans than in mice, making human corticogenesis less vulnerable to ultrasound waves.37 All these questions raise important future research issues.
Continuing research into bioeffects and safety of ultrasonography in pregnancy is warranted. It is essential to examine the possible effects of ultrasound waves on cortical development in nonhuman primates, where the duration of embryogenesis and the size and complexity of migratory pathways are similar to those in humans, as well as to perform comprehensive epidemiologic studies in humans.

[Federvieh]

Proc Inst Mech Eng H. 2010;224(2):363-73.
Ultrasound bioeffects and safety.

ter Haar G.

Joint Department of Physics, Institute of Cancer Research, Royal Marsden Hospital, Sutton, Surrey SM2 5PT, UK. Gail.terHaar@icr.ac.uk
Abstract

The main mechanisms by which ultrasound can induce biological effects as it passes through the body are thermal and mechanical in nature. The mechanical effects are primarily related to the presence of gas, whether drawn out of solution by the negative going ultrasound pressure wave (acoustic cavitation), a naturally occurring gas body (such as lung alveoli), or deliberately introduced into the blood stream to increase imaging contrast (microbubble contrast agents). Observed biological effects are discussed in the context of these mechanisms and their relevance to ultrasound safety is discussed.

PMID: 20349824 [PubMed - indexed for MEDLINE]

Related citations
MeSH Terms

Das hier wäre interessant.

Semin Ultrasound CT MR. 2008 Apr;29(2):156-64.
Safety assurance in obstetrical ultrasound.

Miller DL.

Department of Radiology, University of Michigan, Ann Arbor, MI 48109-0553, USA. douglm@umich.edu
Abstract

Safety assurance for diagnostic ultrasound in obstetrics began with a tacit assumption of safety allowed by a federal law enacted in 1976 for then-existing medical ultrasound equipment. The implementation of the 510(k) pre-market-approval process for diagnostic ultrasound resulted in the establishment of guideline upper limits for several examination categories in 1985. The obstetrical category has undergone substantial evolution from initial limits (ie, 46 mW/cm2 spatial peak temporal average [SPTA] intensity) set in 1985. Thermal and mechanical exposure indices, which are displayed onscreen according to an Output Display Standard, were developed for safety assurance with relaxed upper limits. In 1992, with the adoption of the Output Display Standard, the allowable output for obstetrical ultrasound was increased in terms of both the average exposure (eg, to a possible 720 mW/cm2 SPTA intensity) and the peak exposure (via the Mechanical Index). There has been little or no subsequent research with the modern obstetrical ultrasound machines to systematically assess potential risks to the fetus using either relevant animal models of obstetrical exposure or human epidemiology studies. The assurance of safety for obstetrical ultrasound therefore is supported by three ongoing means: (1) review of a substantial but uncoordinated bioeffect research literature; (2) the theoretical evaluation of diagnostic ultrasound exposure in terms of thermal and nonthermal mechanisms for bioeffects; and (3) the skill and knowledge of professional sonographers. At this time, there is no specific reason to suspect that there is any significant health risk to the fetus or mother from exposure to diagnostic ultrasound in obstetrics. This assurance of safety supports the prudent use of diagnostic ultrasound in obstetrics by trained professionals for any medically indicated examination.

PMID: 18450141 [PubMed - indexed for MEDLINE]PMCID: PMC2390856Free PMC Article

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2390856/?tool=pubmed

Semin Ultrasound CT MR. 2002 Oct;23(5):387-91.
Routine ultrasound scanning in first trimester: what are the risks?

Barnett SB.

CSIRO Health Services Sector, Lindfield, NSW, Australia.
Abstract

Acoustic exposure from modern ultrasonographic devices is capable of disturbing biological tissue to varying extent depending on the type of ultrasound examination and the particular tissue under investigation. There is no strong evidence that these biological effects present a serious health hazard, however, knowledge is incomplete, particularly from human studies. Although ultrasound induced heating can be significant in later pregnancy, it is unlikely that diagnostic ultrasound poses a significant thermal risk to the developing embryo when used according to published safety guidelines. Nevertheless, uncertainties remain, particularly for nonthermal effects in early pregnancy where shear stresses from radiation pressure may become an important factor. The likelihood of producing some biological effects can be enhanced by new procedures such as the use of gas encapsulated echo-contrast agents. The particular sensitivity of the embryo to physical damage together with uncertainties of both risk and benefit suggest that caution should be applied to the scanning of early first trimester uncomplicated pregnancy.

PMID: 12509108 [PubMed - indexed for MEDLINE]

Prog Biophys Mol Biol. 2007 Jan-Apr;93(1-3):331-53. Epub 2006 Aug 4.
Quantification of risk from fetal exposure to diagnostic ultrasound.

Church CC, Miller MW.

The University of Mississippi, National Center for Physical Acoustics, 1 Coliseum Drive, University, MS 38677-1848, USA. cchurch@olemiss.edu
Abstract

Biomedical ultrasound may induce adverse effects in patients by either thermal or non-thermal means. Temperatures above normal can adversely affect biological systems, but effects also may be produced without significant heating. Thermally induced teratogenesis has been demonstrated in many animal species as well as in a few controlled studies in humans. Various maximum 'safe' temperature elevations have been proposed, although the suggested values range from 0.0 to 2.5 degrees C. Factors relevant to thermal effects are considered, including the nature of the acoustic field in situ, the state of perfusion of the embryo/fetus, and the variation of sensitivity to thermal insult with gestational stage of development. Non-thermal mechanisms of action considered include acoustic cavitation, radiation force, and acoustic streaming. While cavitation can be quite destructive, it is extremely unlikely in the absence of stabilized gas bodies, and although the remaining mechanisms may occur in utero, they have not been shown to induce adverse effects. For example, pulsed, diagnostic ultrasound can increase fetal activity during exposure, apparently due to stimulation of auditory perception by radiation forces on the fetal head or auditory structures. In contrast, pulsed ultrasound also produces vascular damage near developing bone in the late-gestation mouse, but by a unknown mechanism and at levels above current US FDA output limits. It is concluded that: (1) thermal rather than nonthermal mechanisms are more likely to induce adverse effects in utero, and (2) while the probability of an adverse thermal event is usually small, under some conditions it can be disturbingly high.

PMID: 16949653 [PubMed - indexed for MEDLINE]

J Ultrasound Med. 2008 Apr;27(4):541-59; quiz 560-3.
Fetal thermal effects of diagnostic ultrasound.

Abramowicz JS, Barnett SB, Duck FA, Edmonds PD, Hynynen KH, Ziskin MC.

Department of Obstetrics and Gynecology, Rush University Medical Center, 1635 W Congress Pkwy, Chicago, IL 60612 USA. jacques_abramowicz@rush.edu
Abstract

Processes that can produce a biological effect with some degree of heating (ie, about 1 degrees C above the physiologic temperature) act via a thermal mechanism. Investigations with laboratory animals have documented that pulsed ultrasound can produce elevations of temperature and damage in biological tissues in vivo, particularly in the presence of bone (intracranial temperature elevation). Acoustic outputs used to induce these adverse bioeffects are within the diagnostic range, although exposure times are usually considerably longer than in clinical practice. Conditions present in early pregnancy, such as lack of perfusion, may favor bioeffects. Thermally induced teratogenesis has been shown in many animal studies, as well as several controlled human studies; however, human studies have not shown a causal relationship between diagnostic ultrasound exposure during pregnancy and adverse biological effects to the fetus. All human epidemiologic studies, however, were conducted with commercially available devices predating 1992, that is, with acoustic outputs not exceeding a spatial-peak temporal-average intensity of 94 mW/cm2. Current limits in the United States allow a spatial-peak temporal-average intensity of 720 mW/cm2 for fetal applications. The synergistic effect of a raised body temperature (febrile status) and ultrasound insonation has not been examined in depth. Available evidence, experimental or epidemiologic, is insufficient to conclude that there is a causal relationship between obstetric diagnostic ultrasound exposure and obvious adverse thermal effects to the fetus. However, very subtle effects cannot be ruled out and indicate a need for further research, although research in humans may be extremely difficult to realize.

PMID: 18359908 [PubMed - indexed for MEDLINE]

[Federvieh]

J Ultrasound Med. 2008 Apr;27(4):597-605; quiz 606-9.
Fetal ultrasound: mechanical effects.

Stratmeyer ME, Greenleaf JF, Dalecki D, Salvesen KA.

Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, US Food and Drug Administration, 9200 Corporate Blvd, HFZ-120, Rockville, MD 20850 USA. melvin.stratmeyer@fda.hhs.gov
Abstract

In this discussion, any biological effect of ultrasound that is accompanied by temperature increments less than 1 degrees C above normal physiologic levels is called a mechanical effect. However, one should keep in mind that the term mechanical effect also includes processes that are not of a mechanical nature but arise secondary to mechanical interaction between ultrasound and tissues, such as chemical reactions initiated by free oxygen species generated during cavitation and sonoluminescence. Investigations with laboratory animals have documented that pulsed ultrasound can produce damage to biological tissues in vivo through nonthermal mechanisms. The acoustic output used to induce these adverse bio-effects is considerably greater than the output of diagnostic devices when gas bodies are not present. However, low-intensity pulsed ultrasound is used clinically to accelerate the bone fracture repair process and induce healing of nonunions in humans. Low-intensity pulsed ultrasound also has been shown to enhance repair of soft tissue damage and accelerate nerve regeneration in animal models. Although such exposures to low intensity do not appear to cause damage to exposed tissues, they do raise questions about the acoustic threshold that might induce potentially adverse developmental effects in the fetus. To date, bioeffects studies in humans do not substantiate a causal relationship between diagnostic ultrasound exposure during pregnancy and adverse biological effects to the fetus. However, the epidemiologic studies were conducted with commercially available devices predating 1992, having outputs not exceeding a derated spatial-peak temporal-average intensity (ISPTA.3) of 94 mW/cm2. Current limits in the United States allow an ISPTA.3 of 720 mW/cm2 for obstetric modes. At the time of this report, available evidence, experimental or epidemiologic, is insufficient to conclude that there is a causal relationship between obstetric diagnostic ultrasound exposure and adverse nonthermal effects to the fetus. However, low-intensity pulsed ultrasound effects reported in humans and animal models indicate a need for further investigation of potentially adverse developmental effects.

So, mir reicht das. Also, bioeffekte sind vorhanden und nicht ausreichend untersucht.

[Daggi]

Das Herumstochern in Primärliteratur bringt nix. Gibts denn nichts zum Thema in Lehrbüchern und Sekundärliteratur?

[Dienstag]

Ja, aber soo unspannend finde ich das auch wieder nicht. Einige Leute gehen ja anscheinend davon aus, dass durch irgendwelche parametrischen Effekte oder so aus dem an sich sehr hochfrequenten Signalen des Ultraschallgerätes Schall im Hörfrequenzbereich entsteht. Und dass es dieser Schall ist, der - möglicherweise - dem Fötus zusetzt. Das ist ohne weiteres möglich, die Frage ist aber, mit welcher Intensität. Interessanter Aspekt.

[heterodyne]

Nachteule, herzlichen Dank, da habe ich viel zu lesen.

die 80 dB das ist eben das, was mit dem Lärm eines einfahrenden Zuges in die Bahnstation verglichen wird...

Much higher peak pressures could be obtained by tapping of abdomen with the fingers.

Interessant

[Federvieh]

Sortiert:

Finde ich auch  

Allerdings habe ich kein Gegenargument außer daß jede Menge Föten friedlich unter Beschallung weiterschlafen bz sich weiter mit den Zehen spielen und dass Ultraschall für einen Menschen nicht zu hören ist, egal wie laut (zB Fledermaus).
Ich kann nur von meiner Erfahrung ausgehen und nicht zB belegen, dass der US im Wasser nicht hörbar wird (sorry, mein Physikunterricht ist einfach zu lange her und Selbstexperiment kann ich mangels Möglichkeiten nicht machen. Ich kann mir nicht vorstellen, dass das passiert, schliesslich müsste der Schall ja dann den Frequenzbereich wechseln) oder aber zB ein Fötus in einem anderen Frequenzbereich hört als ein Baby (ist zwar mMn sehr unwahrscheinlich, aber ich finde nix dazu)

Ja, aber soo unspannend finde ich das auch wieder nicht. Einige Leute gehen ja anscheinend davon aus, dass durch irgendwelche parametrischen Effekte oder so aus dem an sich sehr hochfrequenten Signalen des Ultraschallgerätes Schall im Hörfrequenzbereich entsteht. Und dass es dieser Schall ist, der - möglicherweise - dem Fötus zusetzt. Das ist ohne weiteres möglich, die Frage ist aber, mit welcher Intensität. Interessanter Aspekt.

Ich finde die Frage ebenfalls durchaus faszinierend. Man müßte noch einmal schauen, ab wann das Gehör ausgebildet ist und Schall wahrnehmen kann. Gleichzeitig interessiert mich natürlich, wie hoch der Schallpegel in utero insgesamt ist.

Schallniveau

J Acoust Soc Am. 2005 Mar;117(3 Pt 1):1448-55.
Characteristics of the audio sound generated by ultrasound imaging systems.

Fatemi M, Alizad A, Greenleaf JF.
Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA. fatemi.mostafa@mayo.edu

Medical ultrasound scanners use high-energy pulses to probe the human body. The radiation force resulting from the impact of such pulses on an object can vibrate the object, producing a localized high-intensity sound in the audible range. Here, a theoretical model for the audio sound generated by ultrasound scanners is presented. This model describes the temporal and spectral characteristics of the sound. It has been shown that the sound has rich frequency components at the pulse repetition frequency and its harmonics. Experiments have been conducted in a water tank to measure the sound generated by a clinical ultrasound scanner in various operational modes. Results are in general agreement with the theory. It is shown that a typical ultrasound scanner with a typical spatial-peak pulse-average intensity value at 2 MHz may generate a localized sound-pressure level close to 100 dB relative to 20 microPa in the audible (< 20 kHz) range under laboratory conditions. These findings suggest that fetuses may become exposed to a high-intensity audio sound during maternal ultrasound examinations. Therefore, contrary to common beliefs, ultrasound may not be considered a passive tool in fetal imaging.

PMID: 15807032 [PubMed - indexed for MEDLINE]

J Obstet Gynaecol Res. 1996 Dec;22(6):523-7.
Audible in utero sound caused by the ultrasonic radiation force from a real-time scanner.

Arulkumaran S, Talbert DG, Nyman M, Westgren M, Su HT, Ratnam SS.
Department of Obstetrics and Gynaecology, National University Hospital, Singapore.

While investigating in utero sound levels during vibro-acoustic stimulation on the maternal abdomen it was noticed that noise level increased when the real-time ultrasonic scanner beam was directed at the sensing hydrophone. The noise was recorded and later analysed for frequency content and waveform. It appeared related to the scanning and frame rate frequencies of the scanner used. Sounds may originate from radiation pressure produced when the ultrasound beam is absorbed by tissue or reflected from bone or the metal hydrophone. This implies that although ultrasound cannot be heard per se, any modulation of its intensity will produce vibrations in the maternal tissues or reflecting structures such as skull bone, and especially stapes, malleus and incus, that would be heard as sound by the fetus. The intensity of the sound produced varied with orientation of the transducer beam and this may itself produce a stimulation. Based on our recordings (Fig. 1), it was calculated (please see Appendix) that the fetus would hear a sound corresponding to 84dB noise pressure level in air.

PMID: 9037941 [PubMed - indexed for MEDLINE]

Br J Radiol. 1995 Oct;68(814):1090-4.
An assessment of the intrauterine sound intensity level during obstetric echo-planar magnetic resonance imaging.

Glover P, Hykin J, Gowland P, Wright J, Johnson I, Mansfield P.
Department of Physics, Nottingham University, UK.

In order to assess the sound level experienced by the fetal ear during obstetric magnetic resonance imaging, a fluid filled stomach was used as an experimental model of the gravid uterus. A better than 30 dB attenuation in intensity was recorded across the frequency band of interest for all patient orientations. This was enough to reduce acoustic sound pressure from a level close to the instantaneous damage threshold (120 dB), to an acceptable level (< 90 dB). Direct mechanical coupling through the patient table was also shown to increase uterine sound pressure levels by as much as 10 dB. Much higher peak pressures could be obtained by tapping of abdomen with the fingers.

PMID: 7496710 [PubMed - indexed for MEDLINE]

Obstet Gynecol. 1991 Nov;78(5 Pt 1):803-6.
Vibroacoustic stimulation and intrauterine sound pressure levels.

Nyman M, Arulkumaran S, Hsu TS, Ratnam SS, Till O, Westgren M.
Department of Obstetrics and Gynecology, Karolinska Institutet, Danderyd, Sweden.

The sound pressure level in amniotic fluid generated by vibroacoustic stimulation, assessed with a hydrophone placed close to the fetal head, was studied in 16 subjects. The mean recorded sound pressure level was 115 dB and the highest level was 129 dB. The range of the background noise was 63.5-80.5 dB. There was no obvious relationship between the distance from the stimulator to the hydrophone and the intrauterine sound pressure level. Although sound pressure levels are high, they are probably reduced before reaching the cochlea of the fetus because of the surrounding amniotic fluid and the fluid in the middle ear.

PMID: 1923201 [PubMed - indexed for MEDLINE]

Sieht so aus, als ob der normale Geräuschlevel in utero bei 63,5 - 80,5 dB liegt. Nicht schlecht.