Pregnancy and protection 

of the fetus

Irradiation of a fetus should be avoided whenever possible [18-20, 22].  This includes situations where the woman herself does not suspect pregnancy.  The prime responsibility for identifying such patients lies with the referring clinician.

Women of reproductive age presenting for an examination in which the primary beam irradiates directly, or by scatter, the pelvic area (essentially, any ionising irradiation between the diaphragm and the knees), or for a procedure involving radioactive isotopes, should be asked whether they are or may be pregnant.  If a patient cannot exclude the possibility of pregnancy, she should be asked if her period is overdue.

If there is no possibility of pregnancy the examination can proceed, but if the patient is definitely or possibly pregnant (i.e. menstrual period is overdue) the justification for the proposed examination should be reviewed by the radiologist and the referring clinician, with a decision taken on whether to defer the investigation until after delivery or until the next menstrual period has occurred.  However, a procedure of clinical benefit to the mother may also be of indirect benefit to her unborn child, and a delay in an, essential procedure may increase the risk to the fetus as well as to the mother.

If pregnancy cannot be excluded, but the menstrual period is not overdue and the procedure gives a relatively low dose to the uterus, the examination may proceed.  However, if the examination gives relatively high doses (in most departments, the common examinations in this category will probably be abdominal and pelvic CT, intravenous urography (IVU), fluoroscopy and nuclear medicine studies), there will be discussion in line with locally agreed recommendations.

In all cases, if the radiologist and referring clinician agree that irradiation of the pregnant or possibly pregnant uterus is clinically justified or is not clinically justified, this decision should be recorded.  If it is decided that the irradiation is justified, the radiologist must then ensure that exposure is limited to the minimum required to acquire the necessary information.

If it becomes obvious that a fetus has been inadvertently exposed, despite the above measures, the small risk to the fetus of the exposure is unlikely to justify, even at the higher doses, the greater risks of invasive fetal diagnostic procedures (e.g. amniocentesis) or those of a termination of the pregnancy.  When such inadvertent exposure has occurred, a radiation physicist should make an individual risk assessment and the results should be discussed with the patient.

The RCR has co-authored (with the National Radiological Protection Board (NRPB) and the College of Radiographers) a guidance booklet on the protection of the fetus during the diagnostic investigation of its mother [20]. (This publication is available from the NRPB website at http: / /www.nrpb.org.)

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