Recent expanded availability of fetal ultrasound for bonding/entertainment and a new study indicating effects of ultrasound on the developing mouse brain require a reassessment of safety issues. The ultrasound community, prospective parents and society in general should be more informed, especially about some of the information that many would like to ignore. Although I share the general view that there are probably no significant adverse effects of ultrasound on the fetus, safety should not be treated as a proven fact.
This site was created as a review of material up to January 2007 by Dr. David A. Toms MD FRCPC; updates to 2011 have been added. It is intended to be read sequentially (see downloads) and has been broken into the following navigation.
SUMMARY AND LINKS
There has been about a 1000-fold increase in the time-averaged intensity of ultrasound generated by equipment for obstetrics since around 1980.
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Much of this increase has occurred because of the indifference of medical users to outputs when buying equipment. The opposite trend has been the case in mammography.
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Pressure variations in the ultrasound pulse are large and not intuitively trivial.
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Not all follow-up studies of exposed fetuses are reassuring. Also, the diagnostic intensities used for fetal ultrasound are similar to those used therapeutically in devices that speed up healing of fractures.
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The permissible pulse intensity, as measured by the Mechanical Index (MI), for the fetal eye is up to 1.9 as part of overall exposure regulatory limits. For ophthalmic ultrasound following birth it is 0.23. Why does the fetal eye receive less consideration?
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Dose-dependant effects of diagnostic ultrasound on fluids can be demonstrated with high-resolution probes – see video clips and discussion.
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The medical profession does not have a good record for anticipating the problems its activities can cause.
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I believe that commercial entertainment fetal ultrasound should be discouraged. I also believe that the major causes of needless ultrasound exposure to the fetus are indifference on the part of the medical user community and suboptimal leadership from professional organizations and regulatory authorities with regard to clinical examinations.
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Recommendation
Probably the only way to ensure implementation of the ALARA (As Low As Reasonably Achievable) principle in fetal ultrasound is to encourage patients as well as users to take an interest in equipment issues and output displays.
Please see the Miscellaneous Items/Updates as well as the
above links.
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