Pregnant women should not undergo some medical examinations that involve high doses of radiation to the foetus because of an increased risk of childhood cancer, according to new guidance.
The Health Protection Agency (HPA) said that although the risk was small, pregnant women should not be given ionising radiation in which the foetus receives a dose of more than a few milligrays.
It recommends that certain very high dose examinations where the foetal embryo could receive a dose of more than 10 mGy should not be carried out on early unrecognised pregnancies.
One way of preventing this is to restrict high-dose scans to the first 10 days of the menstrual cycle, when the woman is unlikely to have conceived.
Affected procedures include X-ray CT scans of the pelvis, pelvis and abdomen, pelvis abdomen and chest and CT whole body scans (see attached file).
Most medical examinations, such as X-rays, dental X-rays, CT scans and nuclear medicine scans all tend to involve doses of less than, or much less than 1 mGy.
Risks of childhood cancers associated with these examinations are less than 1 in 10,000 and much lower than the natural rate of childhood cancer (1 in 500).
The guidance, produced by the HPA, The Royal College of Radiologists and the College of Radiographers, updates previous advice issued in 1998.