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A New Pregnancy Policy for a New Era

¹ Department of Radiology, The University of Iowa, Roy J. and Lucille A. Carver College of Medicine, 200 Hawkins Dr., Iowa City, IA 52242.
² West Suburban Hospital Medical Center, Erie at Austin, Oak Park, IL 60302.
³ Present address: Department of Radiology, Boston Medical Center, 88 E. Newton St., Boston, MA 02118.
⁴ Department of Obstetrics and Gynecology, The University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242.

Received September 16, 2002; accepted after revision February 3, 2003.

 
Address correspondence to G. Y. El-Khoury.

Presented at the annual meeting of the American Roentgen Ray Society, Atlanta, April–May 2002.

Introduction

Top Introduction Discussion Conclusion APPENDIX 1. The Pregnancy... APPENDIX 2. Consent Form APPENDIX 3. Consent Form References

 
In a busy radiology practice, encountering pregnant or possibly pregnant patients who require imaging is fairly common. Mann et al. [1] reported that 30% of female patients in a major trauma center were of child-bearing age, and 15% of these patients were either definitely or possibly pregnant. As a result, irradiation of the fetus during diagnostic imaging of the mother is a routine occurrence. Exposing the fetus to ionizing radiation is always an anxiety-provoking problem to patients and physicians alike. This problem continues to be exacerbated by the increased use of high-dose procedures such as fluoroscopy and CT. The number of prolonged interventional procedures performed under fluoroscopic control over the past 10 years has dramatically increased. Concern over the radiation dose from these procedures prompted the United States Food and Drug Administration to issue an advisory warning about the potential for radiation-induced skin burns after interventional procedures [2]. An even bigger concern is multidetector CT, which has become the primary diagnostic tool in the emergency setting. The radiation dose from CT accounts for 40% of the annual collective dose to the public from all medical procedures [3].

Because of the concern over radiation dose to the fetus, radiologists at our institution have been reluctant to use multidetector CT on pregnant patients without careful consideration of other diagnostic options. Some referring physicians have viewed this caution as an infringement on their rights to treat their patients. These concerns were brought before the committee that oversees the diagnostic service in our institution. After exhaustive discussions, it became obvious that establishing a clear policy for imaging pregnant patients was badly needed. Because it has been the traditional role of the radiologist to counsel pregnant patients on the effects of ionizing radiation to the fetus and to advise referring physicians about alternative imaging modalities that can yield similar diagnostic information without the use of ionizing radiation, the department of radiology was charged with the responsibility for developing this policy. Together with input from the radiation physics and radiation biology faculty and the obstetrics department, a pregnancy policy was drafted to achieve the following objectives. First, the policy should protect the mother and fetus, keeping in mind that the well-being of the fetus depends primarily on the well-being of the mother. If the mother's life is at risk and clear indications for an imaging study exist, the examination should not be denied or delayed because of the pregnancy. Second, the policy should encompass all possible clinical situations, and finally, the policy should be clear and easy to implement.

The policy that we have developed is given in Appendix 1, and the informed consent forms that we use are given in Appendixes 2 and 3. In addition, we provide easy-to-use tables that will enable the radiologist to estimate fetal dose for common radiographic procedures. Table 1 gives estimates of fetal doses for radiographic images and fluoroscopy of the pelvis and abdomen for a range of patient body thickness. The fetal dose for fluoroscopic procedures of the abdomen or pelvis with the fetus in the field of view depends on the entrance skin dose. On new fluoroscopic units, the entrance skin dose can be obtained from the dose–area product meter by dividing the measured value by the field size. Fetal dose can be conservatively estimated as 0.15 times the entrance skin dose. Table 2 provides estimates of fetal dose for CT of the abdomen and pelvis.

Discussion

Top Introduction Discussion Conclusion APPENDIX 1. The Pregnancy... APPENDIX 2. Consent Form APPENDIX 3. Consent Form References

 
All diagnostic procedures involving the use of ionizing radiation require a balance between the risk and benefits. Although the risk associated with diagnostic radiation doses to the fetus is low, it is significantly larger than that for the adult. The developing fetus is more sensitive to ionizing radiation, and the time available for the detriment to be expressed is much longer. High radiation doses to the fetus are associated with abortion, body size reduction, mental retardation, and increased incidence of future cancers [4, 5]. However, there are insufficient data on humans to precisely quantify harmful effects on the fetus at doses below 50 mSv (5 rem). Somatic effects such as body size and mental retardation appear to have dose thresholds in the range of 50–100 mSv (5–10 rem) [5–7]. The excess risk for childhood cancer is estimated as 0.06% / 10 mSv (0.06% / 1 rem) [8–10].

Most radiographic imaging studies on pregnant patients have until recently been associated with fetal doses well below 50 mSv (5 rem), leading to the conclusion that the risk of fetal detriment is small. However, there continues to be ongoing investigations into the biologic effects of low-dose irradiation and its safety, especially to the fetus. The potential risk of low-dose radiation in humans cannot be measured directly and is often estimated from linear or linear–quadratic extrapolation from higher doses [11]. Experimental work has recently emerged showing a linear response for the induction of mutations in human cells by X-ray exposures below 100 mSv (10 rem) [12]. New reports on the atomic bomb survivors who were exposed to low-dose radiation (5–100 mSv) have shown an increased incidence of cancer later in life [7, 10]. The Committee on Biological Effects of Ionizing Radiation estimates a 1.2–1.5% increase in cancers for 5-year-old children who received a uniform body dose of 100 mSv (10 rem) [13]. There is also evidence that delivering a dose of 10 mSv (1 rem) to the breast of women less than 35 years old increases their risk of breast cancer by approximately 14% over the spontaneous rate in the general population [14]. Although the identifiable radiation risks are still small, this ongoing work focuses public attention on fetal radiation and adds to the concerns that are raised whenever a fetus is irradiated.

The goal of our policy is to expedite imaging studies when pregnant patients are involved, while limiting fetal radiation dose. Although avoiding radiation exposure to the fetus is desirable, failure to correctly diagnose the medical problems of the mother more often poses a much greater risk to the fetus. Thus, when faced with a pregnant patient, all involved personnel should be prepared with a plan of action that will best address the medical needs of the mother, while minimizing the radiation exposure to the fetus. The implementation of this policy in our radiology department after 1 year has resulted in a significant improvement in the workflow and has established better cooperation between the radiologists and the referring physicians.

Conclusion

Top Introduction Discussion Conclusion APPENDIX 1. The Pregnancy... APPENDIX 2. Consent Form APPENDIX 3. Consent Form References

 
It is important to have a clear policy for handling requests for imaging procedures involving pregnant women. A workable policy should address the concerns of referring physicians, radiologists, and patients. The policy presented in this article attempts to satisfy these needs. With low levels of fetal exposure, the policy allows the examination to proceed without delay. With higher radiation levels, the policy seeks to involve the radiologist, referring physician, and patient to make informed decisions to protect the health of the mother and the fetus. The key elements for making this policy work are education and communication. The radiologist should be aware of the level of fetal radiation doses for radiologic procedures and the magnitude of the associated risks to initiate effective communication with both the referring clinician and the patient.

APPENDIX 1. The Pregnancy Policy

Top Introduction Discussion Conclusion APPENDIX 1. The Pregnancy... APPENDIX 2. Consent Form APPENDIX 3. Consent Form References

 
A. Useful Background Information
The radiation dose to the fetus from conventional diagnostic procedures when the fetus is not in the X-ray beam is approximately the same as the daily background radiation dose received by the average American ( 10 mSv or 1 mrem). The fetal dose from CT or fluoroscopy when the fetus is not in the X-ray beam is typically less than 5 mSv (500 mrem).

Imaging studies such as abdominal radiography, lumbosacral spine examination, and limited excretory urography typically deliver less than 10 mSv (1 rem) to the fetus [5] (Table 1). Examinations in which the fetus usually receives a radiation dose greater than 10 mSv (1 rem) include barium enema, CT of the abdomen and pelvis, and interventional procedures involving lengthy fluoroscopy [5] (Tables 1 and 2).

Because health risks associated with radiation to the fetus are cumulative, previous exposures to radiation must be considered before new procedures are initiated.

B. Identifying the Pregnant Patient
The radiology department should be notified when a patient is known or thought to be pregnant. This information should be stated on the X-ray requisition or entered electronically on the order entry screen.

Before every imaging study or interventional procedure, the technologist should inquire from all female patients of child-bearing age (age range, 12–55 years) whether she is, or may possibly be, pregnant. The radiologist in charge should be notified about any pregnant or possibly pregnant patients referred for imaging. If the patient is too sick to answer questions, the technologist should ask the family or treating physician. If a definitive answer about the patient's pregnancy status cannot be obtained and the patient's condition permits, a pregnancy test should be performed.

C. Clinical Scenarios

1. For examinations of body parts above the diaphragm or below the hips, the patient should be assured that there is no scientific evidence that the examination will result in any detectable harm to the fetus. Shielding of the abdomen and pelvis with lead aprons can be used if feasible, but it is not essential.
   
2. For examinations in which the fetus is in the direct x-ray beam and the estimated dose as determined from Tables 1 and 2 is less than 10 mSv (1 rem), the radiologist should discuss the benefits versus the risks of the procedure with the referring physician. Imaging techniques not involving ionizing radiation such as sonography and MR imaging should be considered. If the examination is judged to be appropriate and necessary, the clinician responsible for the care of the patient should document in the medical record that the imaging study is indicated for the patient management. The radiologist will explain the procedure to the patient and assure her that the risk to the fetus is small. The radiation dose should be kept as low as possible consistent with obtaining the required diagnostic information.
   
3. For examinations in which the fetus is in the direct beam and the estimated dose as determined from Tables 1 and 2 is more than 10 mSv (1 rem) but less than 50 mSv (5 rem), the radiologist and referring physician should discuss other options such as sonography or MR imaging that can provide the needed information without the use of ionizing radiation. If the imaging procedure is deemed appropriate, the patient should be involved in the decision to proceed with the examination. The patient should be informed by the radiologist of the risks and benefits of the diagnostic test or interventional procedure. The patient will be required to sign an informed consent form (Appendix 2). The clinician responsible for the care of the patient should document in the medical record that the test is indicated for the management of the patient.
   
4. For the rare occasion in which the estimated dose to the fetus exceeds 50 mSv (5 rem), a formal calculation of the dose will be conducted by a radiation physicist or equally qualified individual. The patient should be counseled about the risks to the fetus. The referring physician and the radiologist should document in the patient's medical record explaining the circumstances and medical justification for the examination or procedure. The patient will be required to sign an informed consent form (Appendix 3).
   
5. Technical principles to be followed in every pregnant patient:
   
   1. Limit exposures to those that are absolutely essential for the diagnosis.
      
   2. Every effort must be made to eliminate repeated exposures resulting from technical errors. Repeated exposures should not be performed without consulting the radiologist in charge.
      
   3. Precise collimation and pelvic shielding should be used whenever possible.
      
   4. Fluoroscopy should be limited to short bursts as needed. All fluoroscopy procedures must be timed, and a record of the fluoroscopy time, kilovoltage, and milliampere-second must be kept. Newly installed fluoroscopy units have a dose–area product meter that will provide this information. The last image hold and electronic collimation features should be used during fluoroscopy.
      
   5. For CT of the abdomen and pelvis, the radiologist should consider parameter settings that will minimize the fetal dose while yielding useful diagnostic information. Factors that affect the dose include kilovoltage, milliampere-second, acquisition slice thickness, and pitch. Increasing the acquisition slice thickness and pitch and decreasing the milliampere-second and kilovoltage are associated with a significant lowering of the radiation dose ( 50% [15]).
      
   6. As recommended by the International Radiation Protection Association policy, elective MR imaging should be postponed until after the first trimester [16].
      
   7. All contrast media should be used with caution in pregnant women [17].
      
   
   

APPENDIX 2. Consent Form

Top Introduction Discussion Conclusion APPENDIX 1. The Pregnancy... APPENDIX 2. Consent Form APPENDIX 3. Consent Form References

 

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APPENDIX 3. Consent Form

Top Introduction Discussion Conclusion APPENDIX 1. The Pregnancy... APPENDIX 2. Consent Form APPENDIX 3. Consent Form References

 

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References

Top Introduction Discussion Conclusion APPENDIX 1. The Pregnancy... APPENDIX 2. Consent Form APPENDIX 3. Consent Form References

 

1. Mann FA, Nathens A, Langer SG, Goldman SM, Blackmore CC. Communicating with the family: the risks of medical radiation to conceptuses in victims of major blunt-force torso trauma. J Trauma2000; 48:354 –357[Medline]
2. Timins JK, Lipoti JA. Radiation risks of high-dose fluoroscopy. N J Med 2000;97:31 –34
3. Crawley MT, Booth A, Wainwright A. A practical approach to the first iteration in the optimization of radiation dose and image quality in CT: estimates of the collective dose savings achieved. Br J Radiol 2001;883:607 –614
4. Otake M, Schull WJ. Radiation-related brain damage and growth retardation among the prenatally exposed atomic bomb survivors. Int J Radiat Biol 1998;74:159 –171[Medline]
5. Wagner L, Lester R, Saldana L. Exposure of the pregnant patient to diagnostic radiations: a guide to medical management, 2nd ed. Madison, WI: Medical Physics Publishing, 1997:259
6. Otake M, Schull WJ, Lee S. Threshold for radiation-related severe mental retardation in prenatally exposed A-bomb survivors: a re-analysis. Int J Radiat Biol1996; 70:755 –763[Medline]
7. Pierce DA, Shimizu Y, Preston DL, Vaeth M, Mabuchi K. Studies of the mortality of atomic bomb survivors: report 12. I. Cancer: 1950–1990. Radiat Res1996; 146:1 –27[Medline]
8. Doll R, Wakeford R. Risk of childhood cancer from fetal irradiation. Br J Radiol1997; 70:130 –139[Abstract]
9. Kal HB, Struikmans H. Pregnancy and medical irradiation: summary and conclusions from the International Commission on Radiological Protection: publication 84 [in Dutch]. Ned Tijdschr Geneeskd2002; 146:299 –303[Medline]
10. Pierce DA, Preston DL. Radiation-related cancer risks at low doses among atomic bomb survivors. Radiat Res2000; 154:178 –186[Medline]
11. Hall EJ. Scientific view of low-level radiation risks. RadioGraphics1991; 11:509 –518[Abstract]
12. Grosovsky AJ, Little JB. Evidence for linear response for the induction of mutations in human cells by x-ray exposures below 10 rads. Proc Natl Acad Sci U S A1985; 82:2092 –2095[Abstract/Free Full Text]
13. National Research Council Committee of the Biological Effects of Ionizing Radiation. Health effects of exposure to low levels of ionizing radiation: BEIR V, 5th ed. Washington, DC: National Academy Press, 1990: 436
14. Nickoloff EL, Alderson PO. Radiation exposures to patients from CT: reality, public perception, and policy. AJR2001; 177:285 –287[Free Full Text]
15. Golding SJ, Shrimpton PC. Radiation dose in CT: are we meeting the challenge? Br J Radiol2001; 889:1 –4
16. [No authors listed] Protection of the patient undergoing a magnetic resonance examination: International Non-Ionizing Radiation Committee of the International Radiation Protection Association. Health Phys 1991;61:923 –928[Medline]
17. Medical Economics Staff, eds. Drug information for the health care professional, vol. 1, 23rd ed. Greenwood Village, CO: Micromedex, 2003

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