Flying during pregnancy: from radiation to blood clots: everything you need to know

I fly a lot. For work (during my investment banking days), for fun (travel bug) or now as we divide our time between two countries I clock up a lot of air miles. I did this when I was pregnant, and I do this now with my son who we try and take everywhere with us. Question is: given the airport scanners, risk of blood clots during pregnancy and the radiation from air travel (which is much more than from the scanners btw...) is all of this safe?!

As usual - we turn to the science and consider risks for every stage and what you can do to put yourself in a better position.

Luckily one of our expert board advisors Dr Nassim Parvisi specialises in radiology - so here is everything you need to know about air travel for every stage from conception through to travelling with a little one:

Firstly, what is the issue with radiation and flying - where does it come from?

I had heard about ‘radiation’ with air travel and I immediately thought about the scanners - turns out that is not where the real source comes from. Click here for more on why radiation can be a problem and what type, but in a nutshell, the risk, principally, is due to potential damage that it can do to our DNA.

Let’s put it into context: (n.b. Forget the Geiger counter, unless you’re in Chernobyl you measure radiation in ‘microsieverts’):

  • Airport scanner: 0.25 microsieverts

  • Dental X-Ray: 5 microsieverts

  • Flight from New York to Los Angeles: 40 microsieverts

  • Abdomen X-Ray: 200 microsieverts

This chart (credit to Vox for this image) also gives you an idea of how this looks in context of everything else and is a great starting point.

(See chart 1 below)

Where does radiation actually come from when we fly?

Initially I didn't understand how there could be radiation from flying, it honestly didn't make a lot of sense to me….

However, what I learnt is that it is not from the plane, it is from the fact that you’re at altitude and therefore you’re more exposed to what is known as ‘cosmic’ radiation ie. from space.

How does this work? Simply put; when you’re at a higher altitude (average 35,000 feet on a commercial jet) the air is thinner which means there are fewer molecules of gas/volume of space and that means fewer molecules to defect cosmic rays (including those from the sun for example). Essentially it is simply less atmospheric shielding.

This actually means that when you fly it is the duration, the altitude and even how far away you are from the equator (yep...true story!) that matters.

So, the question is: should we worry about flying, when should we worry and what can we do to put ourselves in a better position?

Well there are a few things to consider here:

First and foremost, let’s put this into context. Air travel vs other sources of radiation even when done frequently is far less than smoking for example (phew!) Check out this chart to put it into context - once again credit to Vox here:

(See chart 2 below)

However: if you are pregnant - especially in the early stages - then there are a few additional points to consider:

Firstly, good news! Low does of ionising radiation have NOT been associated with miscarriage, however, doses ‘higher than normal’ within two weeks of conception could potentially present a risk (1)

What is ‘higher than normal’?

A ‘normal’ average person will receive a background radiation level of 3000 microsieverts per year - so that is considered ‘normal’.

Obviously things like x-rays push this number up which is why most doctors and dentists will avoid if you are pregnant or use the lowest possible dose. It also appears that the most sensitive time for miscarriage risk is immediately following conception, so avoiding travel that isnt totally necessary early on is a sensible strategy (3). In fact, another of our expert Board Advisors consultant gynaecologist and obstetrician Mr Mahantesh Karoshi advises his patients to avoid unnecessary flying where possible during the early stages.

That being said, in context, you are not getting huge doses if your travel is infrequent and not too much long haul and later in your pregnancy poses low risk.

What about airport scanners?

If you’re travelling very frequently then lots of this is obviously going to add up, however, the advanced imaging technology x-ray systems that are used actually use very low-dose x-rays, but as per the chart (above) the dose shouldn’t be anything to worry about. That being said, you can always ask for a pat-down which is what I did during my pregnancy - if I wasn’t running for a flight that is… (not recommended if you’re pregnant and trying to avoid stress!)

What about blood clots?

Unfortunately when it comes to developing blood clots there is higher risk while flying if you are pregnant and flying long haul ie. over 4hrs. Pregnant women are at a 5-10x higher risk of developing blood clots (known as thrombosis) vs women who are not pregnant. This actually increases from 20-80x during the post pregnancy period. (2)

What to watch out for?

If you notice pain, swelling or redness in your legs, particularly at the back of the lower leg this could be a sign of a blood clot so seek immediate medical advice.

Ok so using all of this info: how to reduce your risks when flying overall?

When it comes to blood clots:

  • Wear elastic compression flight socks when you fly to improve blood flow.

  • Put them on before you get out of bed in the morning and keep them on until you go to bed following the flight.

  • Ensure you keep well hydrated and take regular sips of water during the flight

  • Pressure in the cabin can make your feet swell so make sure you’re wearing comfortable (and easy to remove) shoes for the flight.

  • Ask for an aisle seat so you can take regular short walks easily around the cabin (and use the bathroom for all that water you’ll be drinking!)

  • Move around (even while seated) as much as possible during the flight

  • Sit or stand for a simple exercise: stretch your leg out - heel first - and gently flex your foot to stretch your calf muscles. While sitting: rotate your ankles in both directions at least ten times.

  • Low dose aspirin is not recommended during pregnancy. (3)

Flying while pregnant more generally:

  • Infrequent (particularly short-haul) air travel is not a major risk.

  • That being said, it is sensible to avoid unnecessary travel, particularly long-haul travel in the earlier stages of pregnancy.

  • Airport scanners are also nothing to get too worried about if used infrequently. If you are concerned, or if you are travelling more frequently, simply as for a pat-down which is well within your rights.

  • Most airlines will not let you fly after week 37 if you are having a single baby (or 32 weeks if you are expecting twins) and remember this applies to how many weeks you are on the day you fly back home.

  • From 28 weeks onwards you will need a signed letter that you are fit to travel (which will include your due date) as the airline may ask for it.

References:

  1. McCollough CH, Schueler BA, Atwell TD, Braun NN, Reiner DM: Exposure and Pregnancy: When should we be concerned? Radiographics: 2007: 27: 909-918

  2. Izadi M, Alemzadeh-Ansari MJ, Kazemisaleh D, Moshkani-Farahani, Shafiee A. Do pregnant women have a higher risk for venous thromboembolism following air travel? Adv Biomed Res 2015; 4:60.

  3. Csorba R, Tsikouras P. Air travel during pregnancy. Hippolratia 2017; 21(1):62.

  4. https://www.nhs.uk/common-health-questions/pregnancy/is-it-safe-to-fly-while-pregnant/

  5. https://www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/air-travel-pregnancy.pdf

  6. https://www.babycentre.co.uk/a6955/flying-while-pregnant  

  7. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/expert-answers/air-travel-during-pregnancy/faq-20058087

  8. Freeman M, Ghidini A, Spong CY, Tchabo N, Bannon PZ, Pezzullo JC. Does air travel affect pregnancy outcome? Arch Gynecol Obstet. 2004;269:274–277.

  9. Chibber R, Al-Sibai MH, Qahtani N. Adverse outcome of pregnancy following air travel: a myth or a concern? Aust N Z J Obstet Gynaecol. 2006;46:24–2