'Parents-to-be should weigh the possible risks of going for non-essential scans purely to get keepsake pictures of their unborn babies,' BBC News reported. It said that while ultrasound scans are 'entirely justifiable and safe, the Health Protection Agency (HPA) is concerned about boutique scanning'.
This is good advice and the most appropriate that can be offered at the current time. Ultrasound has been safely used for diagnostic purposes for 50 years and is an important tool in many areas of medicine. However, with the increasing use of ultrasound for unnecessary souvenir pictures (non-routine antenatal scans) unknown risks may be introduced. As the HPA states, further research is needed to clarify these uncertainties. In the meantime, parents should weigh up these unknown risks against the benefits of having a keepsake enhanced photo of their developing baby.
Where does the news come from?
The advice regarding these souvenir keepsake images or real time ultrasound scans that have no diagnostic benefit has been issued by the HPA.
The advice is based on a review of the evidence on the health effects of ultrasound (frequency above 20 kilohertz) and infrasound (frequency below 20 kilohertz). The review was carried out by the independent Advisory Group on Non-Ionising Radiation (AGNIR), which reports to the HPA.
The main finding is that there is no evidence that ultrasound increases the risk of mortality or cancer to the developing foetus or newborn baby. However, there are some unconfirmed reports that ultrasound could affect the developing nervous system, potentially affecting what would be the child s natural handedness (whether they are right or left handed).
Compared to diagnostic scans that provide a basic image and opportunity for measurements of the baby s growth and development, souvenir scans produce detailed 3D facial images or recordings of the baby s movement in the womb and require prolonged and more intense ultrasound exposure.
What does the AGNIR report say?
The main points of the report are:
- When used for diagnostic medical purposes, which are generally infrequent and for short periods of time, ultrasound does not cause heating or cavitation damage (formation of cavities) in biological tissues, as may be seen with higher levels of exposure.
- A single study in pregnant mice has observed that ultrasound at levels used in medical practice affected the developing nerve cells in the unborn mouse brain. However, the significance of these changes is not known and the study has not been repeated.
- Ultrasound evidence in humans has mainly been concerned with in utero (within the womb) exposures. These studies have found no evidence that ultrasound affects mortality around the time of pregnancy or birth, or has any effect on childhood cancers. In randomised-controlled trials there has been weak evidence that it may affect whether a child is right or left handed (known as handedness), which the reviewers say may be the result of confounding, rather than actual causation.
- When looking at the available evidence for the health effects of low frequency infrasound, (produced by aircraft, trains, thunderstorms, wind, waves and certain machines) there is sparse research. There are also no confirmed biological effects, although at levels above 140dB, hearing damage can occur, for example ear pain or eardrum rupture. Infrasound also has no clear physiological or behavioural effects on humans. Overall, the researchers consider there to be little evidence that infrasound exposure affects humans and no information on its long-term effects.
- Although there are recognised adverse effects from overexposure to ultrasound and infrasound, guidelines and protocols are in place to minimise or avoid this when it is used for medical purposes. Despite there being 'no established evidence of specific hazards' however, there is too little evidence to draw firm conclusions about its long-term effects.
- When regarding diagnostically unnecessary souvenir foetal imaging scans, the unconfirmed reports of possible neurological effects mean there is a need for further research into possible adverse effects.
