Alastair Hay: It is vital America discloses what weapons were deployed

There clearly is a problem in Fallujah as far as the health of newborn children is concerned. Doctors and residents in the city are convinced that many more children than usual are being born with deformities. So great is the concern that some doctors are apparently advising mothers living in the city not to have children. If this is indeed the case the problem could hardly be more serious.

Something has to be done to resolve the issue. It is far from clear if there is a real increase in birth deformities or whether it is a case of more cases being recorded. An answer to this could come by comparing records for births before and after the attacks on Fallujah. For this to be an effective approach full recording of all births would be needed over an extended period.

Another approach is that announced by the World Health Organisation (WHO) on 1 April which is to analyse the trend in birth defects in Fallujah and to compare it with other parts of Iraq. Again good records are required. The comparison may indicate there are problems elsewhere, but it may also find no disturbing trend.

What the WHO will be assessing will be the effects of war on a civilian population, and more particularly what effect a war has on birth outcomes. The investigation is unique and very welcome.

The details of how the investigation is to be conducted are not yet known. If the approach is just to compare trends in birth defects in different locations in Iraq it may not identify causes of these. A more detailed approach would be the logical next step. But if there is no evidence of deformities being greater than the norm why do a more searching inquiry?

But this is jumping the gun. Fallujah has been in the headlines because of the savagery of the fighting there in 2004. US forces used white phosphorus there in November of that year. Allegations have also been made that the US used depleted uranium munitions. It is essential the US says what was used by its forces.

I am not aware of any evidence to suggest white phosphorus or depleted uranium has been linked with birth deformities. However, a toxicologist's reassurance will not be enough for residents in Fallujah and they deserve more. This WHO investigation will help to explain what effects war has on birth outcomes and that has to be a small comfort for clinicians and their patients in Fallujah.

Alastair Hay is professor of environmental toxicology at the University of Leeds