Amaris K. Balitsky
Is performing a chest X-ray during pregnancy considered harmful to the fetus?
Amaris K Balitsky1, MSc., Meldon Kahan, MD1,2 Daphne Williams, MD1,2
1. University of Toronto, Faculty of Medicine, 1 King’s College Circle, Toronto,
Ontario
2. St. Joseph’s Health Centre, Family Medicine/Urban Family Health Team, 30 The
Queensway, Toronto, Ontario
Correspondence: amaris.balitsky@utoronto.ca
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ABSTRACT
Objective: To evaluate the literature on the safety of performing chest X-rays during
pregnancy. Methodology: An Ovid MEDLINE search (from 1967 to present) was
performed using MeSH headings, as listed below. The search was limited to the English
language and human studies. Results: The search yielded 23 articles. Eight articles
were selected. Those not selected included articles about radiation pre-conception,
infants exposed to radiation, or total body radiation. Earlier studies from the 1980’s,
showed increased risk of childhood cancers in children who were exposed to ionized
radiation during pregnancy. These studies included radiation to the abdomen as part of
intrauterine diagnosis. Two reviews revealed that there is no increased risk of
congenital malformation, intrauterine growth retardation, or abortion from low-dose
radiation to the fetus. Maximal risk of 1 rad is 0.003%, which is thousands of times
smaller than spontaneous rates of the above fetal complications. In a study evaluating
prenatal X-ray exposure and rhabdomyosarcoma in children, although there was
increased risk in dental X-rays in first and third trimester, there was no specific
increased risk of chest or abdominal X-rays. In a study on teratogen risk of radiation, it
was found that fetal doses given to head, neck, chest and extremities are extremely low
(<.01 rad) because of the low maternal radiation dose and distance from fetus.
Conclusion: These studies indicate that ionized radiation to the chest during pregnancy
is safe for the fetus in regards to fetal and childhood well-being.
KEYWORDS: pregnancy, X-ray, fetal abnormality
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INTRODUCTION
A case:
A G3P0 28 year old previously healthy female, presented to the family medicine
clinic for her regular prenatal visit at 28+3weeks. She was recently diagnosed with
gestational diabetes, which was effectively controlled with diet. Otherwise, she had no
other pregnancy related complications. As the uneventful visit was wrapping up, the
patient exclaimed, “Oh yeah, I have been spitting up some blood.” The patient had been
to the emergency department two days prior to investigate this new symptom. The
emergency physician decided against a chest X-ray given the “risks to the fetus.”
If this patient were not pregnant and had presented to the ED with hemoptysis,
there would be no hesitation in performing a chest X-ray, in order to necessarily rule out
dangerous and possibly fatal outcomes such as pulmonary embolism. This case was
one out of three occurrences in this physician’s family medicine practice, where
physicians hesitated, albeit with a perceived best interest of the patient in mind, and
failed to perform the appropriate investigations in a pregnant woman for fear of poor
fetal outcomes. A missed or delayed diagnosis can possibly pose a greater risk to a
woman and the fetus than the effects of ionized radiation.
Table 1 highlights the average fetal doses of radiation from various X-ray
procedures. According to Health Canada, the average fetal dose of radiation from a
chest X-ray is less than 0.01 milligrays (mGy)1. To put that number into context, one
could consider traveling by airplane, where cosmic radiation levels are higher than
those at ground level. For example, a round trip between Toronto and Vancouver can
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expose the fetus to 0.05 mGy of radiation, an amount exceeding that of a chest X-ray2.
Travel by air during pregnancy is not restricted until the last weeks of gestation and is
deemed safe by physicians3. Perhaps advice to travel by air is unsound or there is a
misperception of the safety of chest X-rays.
As soon-to-be physicians, we are trained to be cautious when treating a pregnant
woman because there are two lives and a potential family that need to be considered.
We must counsel on issues from immunization status to prevent congenital varicella
syndrome as well as eliminating soft cheeses from the diet for fear of developing listeria.
Are we sometimes inappropriately cautious to the detriment of our patients? Are
necessary diagnostic tests not being performed in pregnant individuals because of
perceived risk or because of a true risk of radiation to the fetus? Our objective was to
determine if a chest X-ray in pregnant women is considered harmful to the fetus.
METHODS
An Ovid MEDLINE search (from 1967 to present) was performed using the
following MeSH headings: 1. Pregnancy; 2. X-ray; 3. Abnormality, radiation induced OR
neoplasm, radiation induced. The search was limited to the English language and
human studies. The search yielded 23 articles, eight of which were selected. Those not
selected included articles about radiation exposure pre-conception, infants exposed to
radiation, or total body radiation. These articles were not suitable for the scope of the
question asked.
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RESULTS
Two of the earlier studies, from the 1980’s, demonstrated an increased risk of
childhood cancers in children who were exposed to ionization radiation in utero 4,5.
These studies, however, included radiation to the abdomen in their group of radiation
procedures (before ultrasound technology was available for use in pregnancy,
abdominal X-rays were used to determine intrauterine diagnoses). Upon closer
examination of these studies, they differentiate between radiation modalities. For
instance, in Shino et al’s (1980) study, the only sub-analyses of each radiation
procedure that showed a significant increase in risk of malignancy was found in mothers
exposed to intrauterine diagnostic X-rays. In a later study evaluating pre-natal X-ray
exposure and occurrence of rhabdomyosarcoma in childhood, they found significantly
higher odds ratios of exposure to a group of radiation modalities. Again, when they
specifically looked at chest x-rays there was no significant increase in risk of the fetus
later developing rhabdomyosarcoma6. These studies may have set a precedent of
general fear of any radiation of pregnant women and poor fetal outcomes.
To address the fear of radiation in pregnant women, the Motherisk group, which
provides information and consultation to women and health-care professionals
concerned about antenatal exposure to drugs, chemicals, radiation, and infection,
concluded that a majority of diagnostic procedures expose the fetus to radiation levels
well below the teratogenic range1,7. Rathapalan and others (2008) emphasized that
when the fetus is not directly in the field of radiation, fetal exposure is a result of indirect
scattered radiation from maternal tissue, and can be further reduced with a lead shield.
When looking at the association of radiation exposure and specific outcomes, CohenUTMJ REVIEW ARTICLE SUBMISSION
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Kerem and others (2006) found no significant increases in still births, prematurity, low
birth weight or major malformations9.
Although a majority of radiation procedures are below the teratogenic range, it
would be helpful in decision making, to know at what dose a procedure is considered
harmful. In assessing how much radiation is truly harmful, a review article looked at
multiple imaging modalities and their associations with fetal outcomes such as
intrauterine growth restriction (IUGR) and congenital abnormalities. They found no
increased risk in either of these outcomes with radiation below 50 mGy8, a number that
far exceeds the fetal dose of 0.01 mGy found from a chest X-ray on a pregnant mother.
Further, Brent (1986) concluded that the maximum risk of 10 mGy exposure causing the
aforementioned fetal outcomes is 0.003%, a rate which is thousands of times smaller
than spontaneous rates of said outcomes. Almost 20 years later, a review evaluating
the risk of the fetus developing IUGR or mental retardation as a child, found that these
outcomes only occurred at doses of radiation that would cause radiation poisoning 9. In
addition, they did not find evidence of any congenital malformations associated with
radiation less than 50 mGy. The dose of radiation found in chest X-rays is convincingly
within safe levels.
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Table 1. Average fetal dose from X-ray procedures (Health Canada)10
Diagnostic type
Average dose (mGy)
Dental
<0.01*
Chest
<0.01
Mammography
<0.05*
Pelvis
1.1
Abdomen
1.4
Lumbar spine
1.7
Natural background radiation (entire pregnancy)
0.5*
Barium meal (Upper GI fluoroscopy)
1.1
Barium enema (fluoroscopy)
6.8
Head CT
<0.005
Chest CT
0.06
Lumbar spine CT
2.4
Abdominal CT
8.0
Pelvis CT
25
*Estimates made by Health Canada
CT: computerized tomography
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DISCUSSION
With a focus on the low dose of ionizing radiation and indirect exposure to the
fetus, the evidence suggests fetal safety when exposed to radiation from chest X-rays.
Compared to spontaneous rates of major malformations (2-3%), IUGR (4%), genetic
disease (8-10%) and spontaneous abortions (15%), a 0.003% risk of poor fetal outcome
when exposed to 10mGy of ionizing radiation is considerably well below those
spontaneous rates8. In a patient presenting with hemoptysis, such as in the case, the
outcome of missing an important diagnosis far exceeds the small risk associated with
0.01 mGy of radiation from a chest X-Ray. Despite the decades of evidence, patients
and physicians are still unaware of the safety of chest X-rays during pregnancy.
These misperceptions of chest X-ray safety can wrongly bias a physician’s care
of the pregnant patient and the patient’s own perceptions of the pregnancy. The
Motherisk group observed a higher rate of pregnancy termination in women who had
been exposed to different forms of radiation11. Upon further investigation, they noted
that these women were terminating their pregnancies for fear of damage to the fetus
from the radiation. Specifically, the women who had radiation procedures perceived a
25% risk of malformation compared to those who had not (16%). After a consultation
session, where experts explained the true risk of imaging procedures during pregnancy,
the perceived risk in the group that did receive procedures dropped to 16.5%11. This
study highlights the importance of education to change the incorrect paradigms, of
radiation and pregnancy, paradigms that were developed during a time when radiation
technology was used in a more harmful way.
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CONCLUSION
Chest X-rays expose the fetus to radiation levels far below the teratogenic range.
This procedure is considered safe during pregnancy and if necessary, it should be
performed. Women who have had X-rays should be reassured that they are safe (i.e.,
there is no need to terminate pregnancy for this reason). Patient and physician
misperceptions about X-rays during pregnancy can bias which investigations are
deemed appropriate. A further study of physician perception of radiation during
pregnancy could further our understanding of how, despite good evidence and Health
Canada guidelines, there is still a misperception regarding its safety.
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REFERENCES
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