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A pregnant patient has a right to know the magnitude and type of potential radiation effects that may result from in-utero exposure. Benefits and risks of the examination should be discussed with the patient, including developmental and cancer risks to the unborn baby. Central nervous system malformations and intellectual deficits have only been reported at fetal doses >100 mSv. Fetal doses from routine medical imaging are generally well below 100 mSv, and are generally below 20 mSv ([https://www.ncbi.nlm.nih.gov/pubmed/22451572]).

[[Radiation therapy]] (whether with external beam, brachytherapy, or nuclear medicine) can involve high radiation doses and may cause harm to the fetus. The risk to the fetus is dependent on the stage of fetal development. Lethal risk occurs in the pre-implantation phase, malformation occurs during major fetal organogenesis 3–7 weeks post implantation, mental retardation occurs at 8–15 weeks post implantation, and future cancer risk follows a stochastic model. Although there is variability in threshold radiation doses, it can be generalised that risks become notable at fetal doses of 100 mGy (10 rad) or above. So, it is essential to ascertain whether a female patient is pregnant prior to [[radiation therapy]]. In pregnant patients, cancers that are remote from the pelvis can usually be treated with radiation therapy. However, this requires careful planning. Cancers in the pelvis cannot be treated adequately during pregnancy without severe or lethal consequences for the embryo/fetus. [[radiation therapy]] in pregnant patients requires pre-therapy fetal dosimetry estimation followed by a comprehensive discussion of the benefits and risks of the procedure, with the patient included as part of the informed consent process.