I once witnessed an obstetrician lay out the pluses and minuses of a pelvic X-ray scan to a pregnant patient. A generation or two ago, it was fairly common to take a radiograph (an X-ray image) to assess for what’s called cephalopelvic disproportion (CPD), which means a fetal head that’s too big to pass through the birth canal. This situation requires a cesarean section, so knowing about it in advance can save the family a lot of apprehension, and protect mother and fetus from potential dangers. But in 1979, North America experienced an event called 3-Mile Island. This is a nuclear power plant in Pennsylvania that had and emergency, and had to shut down. There were no injuries and not adverse health effects, but it got a huge amount of publicity. This corresponded with the release of a movie, The China Syndrome, featuring a dangerous cover-up scenario, Jane Fonda, Jack Lemmon, and Michael Douglas in lead roles, and all the trimmings of a Hollywood thriller. It fueled a kind of radiophobia, a fear of radiation in our society, disproportionate to the actual level of danger.
As a result, there’s a culture in medicine and dentistry that compels providers to “warn” pregnant patients about diagnostic imaging –even when talking about conventional radiography. By conventional, I mean taking single pictures of body parts, as in standard chest-X-rays, dental X-rays, and yes, taking an x-ray or two of the pelvic area, right where the fetus is located.
It is not dangerous, because the dosage of what’s called ionizing radiation is very low from these single films. It’s in the same category of dosage that you receive each year from living on Earth. For high altitude places like Salt Lake City and Denver, that yearly dose is a lot higher. But the people in those places do not experience birth defects, nor do they get cancer, any more frequently than people who live lower down. The only exceptions are skin cancer and cataracts (clouding in the lens of the eye), but that’s due to a kind of non-ionizing radiation, ultraviolet light that’s part of sunlight, which society doesn’t seem to fear as much as it fears radiation that comes from human technology. But regardless of the source, you should not worry about small radiation doses, as our body cells have evolved ways of dealing with it.
Now, if we’re talking about imaging with computed tomography (CT), the issues are very different. What CT does is take many X-ray scans all at once, from numerous directions and angles. This imparts a much higher radiation dose than conventional radiography, so there is real concern in the medical community, and there’s a good rational for avoiding CT scans when possible –especially of the entire body and especially certain types of CT– particularly in pregnant patients. The point here is that dosage matters, just like when you take aspirin.
The patient in the story decided not to have the pelvic X-ray, but she then asked the Ob/Gyn if it would be okay to take an intercontinental flight to Israel. Of course, she meant before hitting the last couple of months of pregnancy, at which point airlines start to get very nervous, because they don’t like to make emergency landings due to a passenger going into labor. The Ob/Gyn said, “Sure, no problem,” but ending the discussion there actually IS a problem, if you’re talking about someone who’s avoiding conventional radiography.
That’s because when you ascend to higher altitudes, as you do in an aircraft, the dosage of ionizing radiation that you receive over time increases, because this radiation is coming in from space. That’s why there’s more of it in Denver than in Los Angeles, although it’s still not a lot in either place. In fact, on the aircraft, the radiation exposure is not a major risk, but it’s important to have an idea of the magnitude.
The dosage of ionizing radiation varies, depending on aircraft altitude and latitude and also on how much the Sun happens to be flaring at the time. On the flight that the patient in my story took, the radiation dosage was equivalent to about one pelvic X-ray film for every 1-2 hours in the air. For an 11-hour flight to Israel, not even including the trip back, that amounts to several pelvic films or chest X-rays, or even more dental X-rays. It also amounts to many thousands of times the dosage that you get from those full-body X-ray scanners at the airport, which use a technique called backscattering, and so the radiation does not even penetrate through your skin.
Just to be crystal clear, the radiation dosage from flying is not a great danger. The point here is to show the concern about conventional radiography, and the full-body scanners at the airport, need not even enter your mind.