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1 Division of Emergency Medicine, The Hospital for Sick Children, 555 University
Ave., Toronto, ON M5G 1X8, Canada.
2 Division of Clinical Pharmacology and Toxicology, Motherisk Program, The
Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.
Received August 13, 2003;
accepted after revision October 29, 2003.
Address correspondence to S. Ratnapalan.
Abstract
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MATERIALS AND METHODS. Structured questionnaires were sent to 400 family physicians and 100 obstetricians selected randomly across Ontario, Canada. The physicians were informed about the 1–3% baseline risk for major malformations and were asked about their perceptions of the risk to the fetus associated with an abdominal radiograph and an abdominal CT scan during early pregnancy and whether they would recommend a therapeutic abortion after such exposure.
RESULTS. Fifty-five percent (218/400) of the family physicians and 69% (69/100) of the obstetricians responded to our questionnaire. Forty-four percent of family physicians estimated the risk associated with an abdominal radiograph to be 5% or greater, and 61% estimated the risk associated with an abdominal CT scan to be 5% or greater. Eleven percent of obstetricians estimated the risk associated with radiographs to be 5% or greater (p < 0.001), and 34% estimated the risk associated with CT scans to be 5% or greater (p < 0.001). Among family physicians, 1% recommended an abortion if the fetus was exposed to radiation from radiography and 6% after exposure to radiation from CT. None of the obstetricians recommended an abortion after exposure to radiation from an abdominal radiograph, but 5% recommended an abortion after exposure to radiation from an abdominal CT scan in early pregnancy.
CONCLUSION. Our survey shows that physicians who care for pregnant women perceive the teratogenic risk associated with an abdominal radiograph and an abdominal CT scan to be unrealistically high during early pregnancy. This misperception could lead to increased anxiety among pregnant women seeking counseling and to unnecessary terminations of otherwise wanted pregnancies. This perception of high teratogenic risk associated with radiation could also lead to a delay in needed care of pregnant women.
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The teratogenicity of radiation is dose-dependent. Radiation exposures greater than 500 mGy cause fetal damage [5]. The most vulnerable period for radiation-induced central nervous system damage is 8–15 weeks after conception. Adverse fetal effects associated with radiation exposure include small head, mental retardation, intellectual deficits, or induction of childhood malignancies. Exposure to less than 50 mGy has not been shown to be associated with differences in pregnancy outcomes when compared with a control population who received only background radiation [5]. Background radiation varies slightly depending on altitude and latitude, but an embryo usually receives less than 1 mGy of background radiation during the 9 months of gestation [5].
The United States National Council on Radiation Protection states that the risk of induced miscarriages, malignancies, or major congenital malformations in embryos or fetuses exposed to doses of 50 mGy or less is negligible compared with the spontaneous risk in the nonexposed [6]. Spontaneous risk includes a 15% chance of having a spontaneous abortion, a 3% risk for a major malformation, and a 4% possibility of restricted fetal growth [7, 8]. The radiation safety committee of the Centers for Disease Control and Prevention of the United States Department of Health and Human Services recommends that unborn babies of laboratory workers should not be exposed to more than 500 mrem (5 mGy) cumulatively during the entire gestational period [9]. This occupational exposure guideline is one tenth of the safe dose and should not be confused with the teratogenic threshold.
The term "radiation" appears to be associated with alarm; it is often correlated with the known adverse biologic effects resulting from the atomic bombing of Hiroshima and Nagasaki during World War II and the incident at Chernobyl [5, 7]. A survey conducted by the Motherisk Program informed pregnant women exposed to ionizing radiation that the baseline risk of major malformations in the general population is approximately 3% and then asked about their perceptions of the risk for fetal malformations. Women who underwent diagnostic imaging procedures assigned a 25.5% teratogenic risk for major malformations, and a nonexposed control group assigned a 15.7% teratogenic risk associated with diagnostic imaging procedures in pregnancy [10]. A 1993 questionnaire survey conducted in Israel showed that 40% of family physicians (n = 86) and 70% of obstetricians (n = 20) recommended therapeutic abortion for women exposed to radiation from diagnostic imaging procedures in early pregnancy [11]. This study did not address a threshold dose or the estimated risk for recommending therapeutic abortions.
To our knowledge, no information about North American obstetricians' or family physicians' perceptions of teratogenic risk associated with exposure to radiation from radiography and CT during early pregnancy has been published. Considering the number of women who may undergo diagnostic imaging procedures during early pregnancy, we believe that it is important to know how physicians caring for pregnant women perceive teratogenic risk and assess the decisions they may make on the basis of these perceptions. The objective of this study was to determine family physicians' and obstetricians' perceptions of the risk of major fetal malformations associated with exposure to radiation from radiography and CT during early pregnancy.
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5%) and 100 obstetricians (
10%) across Ontario were randomly selected through computer-generated random
numbers from the physicians' Canadian Medical Directory
[12], and a structured
questionnaire along with a cover letter was sent to them. The physicians were
informed about the 1–3% baseline risk for major fetal malformations and
were asked about their perception of fetal risk associated with an abdominal
radiograph (kidneys, ureters, and bladder) at 6 weeks of gestation, their
perception of fetal risk associated with an abdominal CT scan at 6 weeks of
gestation, and whether they would recommend therapeutic abortions on the basis
of their perceptions of teratogenic risk. Current information about radiation
exposure during early pregnancy was sent to all respondents. The chi-square
test or Fisher's exact test was used to analyze nominal data. |
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Forty-four percent of family physicians and 11% of obstetricians estimated the teratogenic risk associated with an abdominal radiograph to be 5% or greater (p < 0.001) (Table 1). Sixty-one percent of family physicians and 34% of obstetricians estimated the teratogenic risk associated with an abdominal CT scan to be 5% or greater (p < 0.001) (Table 2). There was no significant difference between the physicians who estimated the teratogenic risk associated with radiography or CT as 5% or greater versus those who estimated the risk to be less than 5%.
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Among family physicians, 1% recommended an abortion if exposed to radiation from an abdominal radiograph (estimates of teratogenic risk: 50% and 90%), and 6% recommended an abortion if exposed to radiation from an abdominal CT scan during early pregnancy (estimate of teratogenic risk: range, 5–100%). None of the obstetricians recommended an abortion after exposure to radiation from an abdominal radiograph, but 5% recommended an abortion after exposure to radiation from an abdominal CT scan during early pregnancy (estimates of teratogenic risk: 10%, 25%, and 25%) (Table 3).
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Among obstetricians, no significant difference was apparent between the respondents and nonrespondents in terms of male–female ratio, number of years in practice, or university affiliation. However, significantly higher numbers of female physicians (p = 0.01), physicians with less than 10 years of practice history (p = 0.03), and physicians without university affiliation (p < 0.001) were among the family physicians who responded to the questionnaire than among those who did not respond.
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The radiation dose to the fetus is estimated to be equal to the dose delivered to the uterus. Most diagnostic imaging examinations result in less than 50 mGy of radiation to the fetus. An estimate of the radiation dose used for a particular study can be obtained from most institutions. The estimated fetal exposure for a typical abdominal radiograph (kidneys, ureters, bladder) is 2.5 mGy, and it is 30 mGy for an abdominal CT scan [13]. No significant increase in major fetal malformations in pregnant women who were inadvertently exposed to these radiation doses has been observed, and these women should be counseled appropriately [5, 7, 8, 13]. In general, fetal radiation doses exceeding 150 mGy between the second and 15th week of conception may be an indication for therapeutic abortion [14]. Fetal doses of less than 50 mGy are considered minimal therapeutic risk and do not justify therapeutic abortion. Therapeutic abortion may be considered for a fetal radiation dose between 50 and 150 mGy only if other compromising circumstances exist [14].
Although minimizing radiation exposure to pregnant patients is always prudent, it is equally important that inadvertently exposed patients are counseled appropriately so that their anxiety and ignorance can be alleviated. Most pregnant women consult their family physicians or obstetricians to allay anxiety regarding radiation exposure. A perception of high teratogenic risk by responding physicians when there is none is of concern. This misperception could be due to various factors, one of them being the lack of knowledge about radiation doses as shown by a recent survey [15]. Even if one assumes that all the nonrespondents would have accurately estimated the teratogenic risk, more than 30% of family physicians and more than 20% of obstetricians would have overestimated the risk of major congenital malformations. Although the numbers are small, our finding that physicians who care for pregnant women would recommend an abortion on the basis of an overestimated teratogenic risk is worrisome. Most family physicians who recommended an abortion estimated the risk to be 50% or greater (7/11), and all obstetricians who recommended an abortion estimated the risk to be 10% or greater (5/5). One family physician recommended an abortion on the basis of a 5% teratogenic risk estimation. It is interesting to note that 29 family physicians and 11 obstetricians were reluctant to estimate the teratogenic risk associated with an abdominal CT scan and wrote "don't know"; 13 family physicians and six obstetricians responded "don't know" for risk associated with an abdominal radiograph. None who responded "don't know" recommended abortions.
In this study, we examined physicians' attitudes, but attitudes do not necessarily translate into behavior. We did not ask the physicians for their views about abortion or their opinions about therapeutic abortions for other medical indications. It would have been informative to know whether the respondents have a threshold teratogenic risk that they regard as an indication for recommending an abortion. One could postulate that any overestimation of teratogenic risk above the baseline would make the physicians reluctant to reassure the mother about the safety of her unborn baby.
In conclusion, our survey shows that Ontario physicians who care for pregnant women perceive teratogenic risk from radiation to be unrealistically high. This misperception could lead to increased anxiety among pregnant women seeking counseling and unnecessary terminations. The perception of high teratogenic risk of radiation could also lead to a delay in needed care of pregnant women. Organizations that make recommendations about radiation doses should address this problem and increase physicians' awareness of radiation doses and effects. Educational intervention such as discussions about radiation doses and effects in radiology seminars, continuing education courses for physicians caring for pregnant women, and review articles in general medical journals should be considered to facilitate accurate estimation of radiation risk by physicians.
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