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Ultrasound in pregnancy - not as safe as you think?

Many years ago (1980s) questions were raised about the safety of ultrasound scans for the unborn baby. Concerns centred around an effect which had been observed when cells were bombarded with ultrasound waves at levels used for visualisation. It was noted that cells that were normally arranged in orderly rows became jumbled up and erratically organised. This led to speculation that growth may be affected - cells in the developing fetus that were. not in neat alignment may grow haphazardly, perhaps resulting in a smaller size of the baby. This proposition was reinforced by a landmark study done in Western Australia by Dr John Newnham who was investigating the effects of serial ultrasound scans during pregnancy on the baby. He found, unexpectedly, that those babies scanned more than twice were smaller than those scanned less often - not a great difference (around 30 grams) but still significant.

Another concern raised was the impact that scans might have on the ova present in unborn baby girls. These cells are fully developed in the ovary very early in pregnancy (around 8 weeks) and it was suggested that ultrasound waves that disorganised these specific cells may have later ramifications for fertility. This proposition has not been tested (to my knowledge) but makes sense from a biological perspective.

The simple fact is that there is very little evidence of the long term effects of ultrasound scans on the baby during pregnancy. It is clear that there are no major effects, since these would have shown up quite early but more subtle effects, like a tendency towards left-handedness have been demonstrated in babies who were subjected to several scans before being born. Less obvious impacts, such as smaller stature, impaired fertility etc would take considerable effort to investigate fully, and there just doesn’t seem to be enough concern or incentive (or resources) to undertake this work.

At the same time, there is an increasing market for scans and the equipment being used is becoming much more advanced and powerful. These days 3-D ultrasounds can provide a very clear picture of the baby, and to achieve this prenatal snapshot, the baby must be subjected to much higher intensities of ultrasound waves for longer periods. Shop front ultrasound stores have sprung up, encouraging expectant parents to get early pictures (even movies) for their albums, and the operators of this highly sophisticated equipment may have no medical training.

Recent articles in the British press have highlighted this development and warned parents that they may be exposing their babies to unnecessary risks and unknown consequences when they buy these images. After years of promoting ultrasound as “safe”, the medical profession is finally admitting that there are potential problems with overexposure to ultrasound waves in pregnancy. Parents don’t often realise that the hand held sonicaids and dopplers used to listen to the bay’s heartbeat also use ultrasound and that the information provided by electronic fetal monitoring, which is heavily relied on to measure fetal well being during labour is also acquired through continuous ultrasound waves beamed at the baby, often for many hours. Baby’s developing systems are therefore experiencing ultrasound waves quite frequently, adding up to a considerable level of exposure over the entire pregnancy.

Various medical bodies in the US, UK and Australia have warned of over exposure and suggested that pregnant women limit their scans to two during pregnancy. However, the seductive nature of the advertising, the natural curiosity of pregnant parents and the money making opportunities presented by ultrasound scans (for doctors and shop-front operators) are powerful influences.

As one of my colleagues noted in a wry comment on the Australian midwifery email list, “I've personally wondered if ultrasound isn't a way that will naturally limit white middle class populations. A ready built population control mechanism. One way of dealing with the crazy consumerism plague of western civilisation.” She might be onto something there!

More useful information can be found in in "Ultrasound Unsound".

Posted by andrea at August 09, 2006 01:05 PM