Radiation and pregnancy

My kids look perfectly normal – in my humble opinion maybe even a tad better than normal. This became an issue, actually, in the months following the 2002 arrest of Jose Padilla on charges he was plotting to set off a “dirty bomb.” How it became an issue is that I was interviewed by a reporter interested in the reproductive effects of radiation – she was wondering if we could expect to see legions of children born with birth defects in the aftermath of a radiological attack. I spent a fair amount of time helping her to understand the basic science behind why this was unlikely to happen and then, to lighten the conversation a bit, threw in the line “let’s face it – if parents have strange-looking kids they should probably blame the in-laws and not the radiation.” Guess what line was quoted. For a few weeks I was getting e-mails from colleagues around the world asking to see photos of my kids. And I’m happy to say that in spite of my years working around radiation, my kids look perfectly normal. At least as close to normal as we can expect from teens….

Of course, my kids’ appearance is not the point – the point here is that the reproductive effects of radiation are exaggerated to the point of irrationality – more so than virtually any other reproductive hazards. True – radiation can cause birth defects and it has been shown to induce mutations in animals. But the amount of radiation required to cause birth defects in humans is substantial (at least 5 rem or 50 mSv to the fetus) and the medical literature has not noted a single instance in which pre-conception radiation exposure to humans has caused birth defects when the woman eventually conceives. And if more people – physicians included – really understood these points there would be far fewer worries.

Consider – the BBC documentary Nuclear Nightmares (which was about radiation phobia) stated that the Soviet government performed a few hundred thousand abortions on women exposed to radiation after the accident and others have stated that there were at least 100,000 abortions conducted in Europe due to fears about the reproductive effects of radiation exposure. It is almost certain that few – if any – of these abortions could have been justified by the radiation exposure alone. I understand that the numbers cited are not from the peer-reviewed literature and that they might be exaggerated (although I have spoken with some who claim that the actual numbers are far higher). But the 2006 report by the World Health Organization concluded that after 20 years there had been fewer than 100 deaths attributable to radiation exposure from the accident (including radiation-induced cancers) and projected that as many as 10,000 people might eventually develop cancer from the accident – even if the WHO’s worst-case estimates come to pass and even if the abortion numbers are over-stated by a factor of 10 we will still find that fear, lack of understanding, and misinformation was deadlier than the accident itself. This is tragic.

As a medical radiation safety officer I calculated nearly 100 fetal dose estimates, usually when a pregnant woman was involved in a car crash and, while unconscious, received the “trauma series” of x-rays from head to foot, possibly followed by CT or even fluoroscopy. Sometimes when the woman woke up she told the doctor she was pregnant, sometimes she didn’t know this herself for another few weeks. In either case, our policy was that I was to be informed so that I could perform fetal radiation dose calculations and write a letter explaining the results to the woman’s OB/GYN. There was not a single case in which the fetal dose estimate was high enough to warrant taking any actions at all, even though some of the women had been advised they might need to terminate their pregnancies. And I was not alone in this – the Health Physics Society runs a wonderful feature on their website (Ask the Experts) that has a section for radiation and pregnancy. Over the last decade or so they have accumulated hundreds of inquiries on this topic and almost none of them warranted any concern at all. Sadly, many physicians in the US are taught that radiation can cause problems with pregnancy, some of them might vaguely remember a dose of 5 or 10 rem (50-100 mSv) can cause problems, but don’t know the fetal radiation dose from the radiation they might prescribe, and are then told little more. Is it any wonder they sometimes give bad advice?

The Centers for Disease Control and Prevention maintains an informative web page that includes information on the impact of prenatal radiation exposure aimed at parents and at physicians. CDC includes a table that summarizes the impact of prenatal radiation exposure based on the post-conception age and the fetal radiation dose – they conclude that for any radiation exposure that occurs less than 2 weeks into the pregnancy and for any fetal radiation exposure of less than 5 rem (50 mSv) there is no need to take any actions at all. To put this number in perspective, it can take tens of x-rays or a few CT scans that image the uterus (the exact number depends on the x-ray or CT machine being used, the amount of tissue between the x-ray beam and the fetus, and a number of other factors) to reach this level of fetal exposure. And for x-ray exposures that do not image the uterus – a chest or head x-ray for example – the dose is even smaller. But believe it or not, I even took a call from a woman who had dental x-rays wondering if she should take her physician’s advice to have a therapeutic abortion.

Having said all of this I don’t want to make it sound as though I’m advocating throwing caution to the winds – according to the ALARA principle (to keep radiation exposure As Low As Reasonably Achievable) we should not simply run up the dose through unnecessary medical imaging – I agree with the goals of the Image Gently initiative to help reduce pediatric (and prenatal) radiation exposure. But I would suggest that if the mother’s health or life are at stake then physicians should avail themselves of the tools they have without letting unwarranted fears deny them access to valuable diagnostic information. And the physicians need to remember that – before giving any medical advice about the pregnancy – fetal radiation dose should be calculated by a qualified and competent health physicist or medical physicist. Radiation health effects depend on the radiation dose – absent a solid radiation dose estimate it simply is not possible to give good, informed advice to the prospective parents.

At this point I feel I should state unequivocally that I am not attacking physicians in this or in my earlier posting. Two of my great-uncles were physicians and I have worked with a huge number of physicians in my professional career. Most physicians will never have to deal with a pregnant woman exposed to radiation – this lack of experience plus the fact that medical schools do not normally teach their students about the medical or reproductive effects of radiation helps to explain physicians’ relative lack of knowledge in this area. I honestly believe that physicians try their utmost to give solid, science-based medical advice whenever possible and most of them do what they can to give their patients the best advice possible.

The sad fact is that the programs that train our physicians – not just in the US by the way, remember the numbers from Europe – are not doing a good job of teaching their students about the impact of radiation on their patients. I discussed this in an earlier blog, where you can find references on this point. This is ironic given that, according to the National Council on Radiation Protection and Measurements, our exposure to medical radiation has increased dramatically in the last few decades. Given our society’s heavy reliance on radiation in industry, medicine, research as well as our dependence on nuclear power, I would like to think that our physicians can be better prepared to give good advice to their patients about the effects of the radiation to which they are unavoidably exposed, just as I would like to think that the public can be provided with solid information so that they can participate more fully in the process of making decisions about radiation exposure.


Dr Y is a certified health physicist, trained in nuclear power plant design and operations, with experience in nuclear power, environmental science, and planning for radiological and nuclear emergencies. He has 30 years of experience in the areas of nuclear and radiation safety, including managing an academic/medical radiation safety program at a major research university and hospital.

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6 Responses to “Radiation and pregnancy”

  1. Mary Olson January 13, 2012 at 12:03 PM #

    Dr Y, Interesting piece. Too many points to reply to…but I would like to know your citation for this statement:
    “But the amount of radiation required to cause birth defects in humans is substantial (at least 5 rem or 50 mSv to the fetus)” I assume that this is a human-based sample? If not, what was the species used?

    AND I would also like a reference to the body of work that enables someone as yourself to express with 100% conviction that any given abnormal birth categorically did not result from radiation exposure if there is no showing of this level of radiation administered.

    I believe if you read the National Academy of Sciences, BEIR reports (Biological Effects of Ionizing Radiation), most notably BEIR VII, as flawed a piece of work as it is, it does substantiate that there is no threshold of ionizing radiation exposure below which harm cannot result.

    As a student of the field, I will tell you that it is not so much “defects” that you might be concerned about as 1) catastrophic impacts resulting in either spontaneous abortion or apparent infertility…or alternately, childhood cancer. Dr Alice Stewart, who it appears you have forgotten (Oxford in the 1950′s), called childhood cancer and leukemia “post-birth defects” from radiation harm to the fetus.

    Finally, you might want to have as much concern for your wife and your daughters… the same BEIR VII data shows that adult women have a 50% higher incidence of cancer and 50% higher cancer mortality compared to adult men at the same level of exposure to ionizing radiation — some of this exposure comparable to doubling “background” — 100 milli-rads a year over a lifetime. See: http://www.nirs.org/radiation/radhealth/radiationwomen.pdf, a briefing paper I wrote on this matter entitled “Atomic Radiation is More Harmful to Women.”

    • Dr. Y January 13, 2012 at 6:44 PM #

      Mary – many thanks for your thoughtful comments. I can’t reply in depth right now as I’m about to leave for the airport, but I didn’t want you to have to wait until Monday for any reply at all. So let me say a little now with more to follow!

      The 5 rem/50 mSv threshold for birth defects is stated on the CDC website and also in a paper by Dr. Robert Brent, published in a book “The Biological Basis for Radiation Protection Regulations” (or something like that – I’m going from memory). In a personal conversation Dr. Brent stated that birth defects are deterministic effects and, as such, they do not occur below a threshold dose.

      In a presentation to the Health Physics Society within the last decade (again I’ll have to look up the exact date) Dr. Brent also noted that there are some birth defects that radiation does not cause. These include assymetric birth defects as well as conditions such as neural cord defect, trisomy, and so forth.

      With regards to the possibility that in utero radiation exposure can increase the risk of childhood cancer, this is correct, although the risk factor is far lower than most would expect. Children (in and out of the womb) are more susceptible to radiation than are adults by about a factor of 2-3 depending on the site of the cancer (according to the BEIR VII report). However, doubling a very low risk still gives you a very low risk (take a look at my posting on airport scanners). And for radiation exposures of less than 5 rem the Health Physics Society notes that it is inappropriate to calculate a numerical risk estimate because the epidemiology is so inconclusive. Other organizations (the National Council on Radiation Protection and Measurements, the International Commission on Radiation Protection, and the United Nations Science Committee on the Effects of Atomic Radiation) have all published reports stating that they assume for the sake of conservativeness that the Linear No-Threshold hypothesis is correct but that the scientific data do not rule out the existence of a threshold or even beneficial effects.

      That’s all that I really have time for now – and I apologize for not including links and more formal citations to back up these statements. I’ll try to do better when I return next week. And thanks again for your comments!

  2. Mary Olson January 14, 2012 at 2:03 PM #

    Thank you for a prompt reply. I will look back here for the links. I am interested.

    In the interim, I do think it is a little worrying to me that your title is “Radiation and Pregnancy” and you have chosen to focus almost soley on deterministic issues in the original post, while now acknowledging stochastic impacts as well.

    I will go to my library as well and see if I can give you some reality-based numbers from the epidemiological world. Dr. Stewart for instance clocked a 400% increased risk of childhood leukemia from an X-ray to the mother…but I am pretty sure that the 1950 X-ray is bigger than a typical X-ray now… so will try to find apples to compare to apples.

    In any case I strongly disagree with your call to doctors to be “less worried” — no, people should not stress out unnecessarily, but I do not think there is ANY reality-based data to support that idea that we should be giving unborn developing fetuses MORE radiation…and personally, I support the trend towards less and less in all radiological procedures thanks to digital imagery and other efficiencies!


  3. Dr. Y January 16, 2012 at 11:24 PM #

    Mary -

    I really don’t think we are too far apart in our views on this. I agree that we should not do what we can to minimize radiation dose to everyone – especially to children and to pregnant women. But what concerns me is that many parents and physicians are too ready to call for terminating a pregnancy due to radiation exposure when there simply is no call to do so. After a single CT scan the risk of having a baby with birth defects is zero, the risk that the child might develop cancer is very low, but the risk to the child from terminating the pregnancy is 100%.

    It also concerns me that sometimes the risks from radiation are given more weight than is warranted and this sometimes leads parents and physicians to take actions that are unwise. At my hospital, for example, we had parents refusing to permit CT scans for their children – in favor of exploratory surgery. Again, the risks of the surgery are greater than the risks from the radiation exposure.

    If anything I would say that I am calling for physicians and parents to be less worried because both groups tend to over-estimate the risks from radiation exposure. I am not calling for them to be cavalier – please note that I do support the “image gently” program! What I think is vitally important, however, is to give radiation the respect it is due – no more and no less.

    Finally, I understand that Alice Stewart had some serious concerns about the reproductive impact of radiation. However, I don’t think that much of her work stands up well over time and I don’t believe that her results have stood the test of time. In particular, you might be interested in a summary of work performed by the ICRP on the effects of fetal radiation exposure (www.icrp.org/docs/ICRP_84_Pregnancy_s.pps).

    The ICRP states that there is no indication of birth defects for any fetal dose of less than 10 rem (100 mSv)and that, even at this dose, the risk of leukemia is less than 1%. This is consistent with the conclusions presented at the 1997 meeting of the National Council on Radiation Protection and Measurements – the Proceedings of this meeting were published in the April 1999 issue of the scientific journal Teratology (http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1096-9926(199904)59:4%3C%3E1.0.CO;2-Y/issuetoc).

    I think that it you put all of this together you will find a more nuanced view of this issue than Alice Stewart presents in her papers – and also more nuanced than I might have presented in my initial posting. Again – I don’t think that we should throw caution to the winds and image willy-nilly. But I also don’t think that physicians should withhold necessary diagnostic procedures (and should certainly not advise a therapeutic abortion) based on exaggerated fears or caution about the effects of radiation on the pregnancy.

  4. Surgeon August 16, 2012 at 10:25 PM #

    Hello, thank you for the information. I am a general surgeon and pregnant with my 3rd child. I am pretty early, about 5 weeks – but I do fluoroscopy during lap chole’s and port placements. I wear lead front and back. Anything else I should or should not do. Before with my other pregnancies I avoided the port cases but still had to do the fluoro in gallbladder cases. Thanks for the input.

    DR. Surgeon

    • Dr. Y August 17, 2012 at 12:44 AM #

      Glad I could help! During my years as Radiation Safety Officer I only rarely felt I had to advise our physicians to change their work habits when they were pregnant – the only ones were those who did a LOT of fluoroscopy (cardiac catheterization laboratory and interventional radiology) and those who worked with a lot of I-131 in nuclear medicine. But less intensive use of x-ray and fluoroscopy is usually not a problem. And, if nothing else, wearing a fetal badge beneath your lead apron will let you keep track of radiation dose to the baby. Good luck!

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