Parents-to-be have been told to think twice before having "souvenir" ultrasound scans of their unborn babies.

Earlier this month, the UK Health Protection Agency's Independent Advisory Group on Non-Ionising Radiation (AGNIR) cautioned against the rise in these keepsake scans. It added that more research was needed into the possible adverse effects of ultrasound on foetuses.

It seems logical that ultrasound could pose a risk to foetuses due to increased levels of sound and heat during scans. Although it has not been confirmed, ultrasound could affect the developing nervous system, and has been linked to higher rates of left-handedness in boys. Some even claim that it could cause other neurological problems such as autism, dyslexia and epilepsy.

When the scan has a medical purpose, such as picking up birth defects, the benefits are likely to outweigh these risks, the AGNIR concluded. The panel added that the available evidence does not point to an increased risk of mortality or childhood cancer with diagnostic ultrasound.

In light of the risks, souvenir scans are frivolous at best, and could even be dangerous. But this doesn't seem to have deterred parents eager for a memento to put in the baby album.

The problem is exacerbated because keepsake scans often take longer than diagnostic scans, in order to get a good image of the baby. They may also be carried out by operators without a medical background.

It's not just the UK that has this problem: last year, the US state of Connecticut took measures to limit obstetric ultrasounds to medically necessary procedures (www.clinica.co.uk, July 28 2009).

At the time, it was reported that these procedures could take as long as 30 minutes, and there were also claims that at least one woman had 19 non-medical ultrasounds taken during her pregnancy. This is an extreme case, but highlights the fact that some people might not be taking the risks associated with ultrasound seriously enough. Hopefully the recent AGNIR report will encourage more people to do so.