Rant: Imaging Women in Trauma

It’s 0200. You’re the only doctor in a hospital five hours from the nearest trauma centre. A 24-year-old woman arrives via ambulance after a high-speed rollover. GCS 14. HR 118. BP 94 systolic. Seatbelt sign across the abdomen. She says she might be pregnant — maybe six weeks, maybe not at all. She’s not sure.

And somewhere in the room, the hesitation begins.

Not in you, necessarily. But you’ve felt it. The half-second of oh when a young woman arrives after a significant mechanism. The faintly spoken concern from a nurse. The instinct — culturally baked in, not evidence-based — to go carefully because of a possible early pregnancy. The creeping thought: what if I harm the baby?

I want to talk about that hesitation. Because it has a body count.

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The problem isn’t radiation. The problem is us.

In 2024, a study of emergency department physicians found that 88.7% reported finding the management of pregnant trauma patients challenging, and expressed a preference to avoid these cases. Nearly nine in ten. Not first-year residents — physicians. And the consequence was exactly what you’d predict: delays, selective under-imaging, and practice variability that had nothing to do with the evidence and everything to do with discomfort.

Trauma is the leading non-obstetric cause of maternal death. Motor vehicle collisions account for more than half of trauma in pregnant women. The fetus does not survive maternal exsanguination. There is no version of this story where protecting the fetus means under-resuscitating and under-imaging the mother.

The best treatment for the fetus is optimal treatment of the mother. This isn’t a controversial statement. It’s in ATLS. It’s in the ACOG guidelines. It’s in the ACEM/RANZCR joint imaging guidelines. It’s the unanimous position of every relevant professional body on the planet. And yet here we are, with 88.7% of emergency physicians describing a preference to avoid these patients.

That’s not caution. That’s a knowledge gap dressed up as sensitivity.

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Let’s actually talk about the radiation.

The fear is deterministic effects — the real, measurable harm that radiation causes to a developing embryo. Microcephaly. Organ malformation. Growth restriction. Death of the conceptus. These are real. They happen. And they have a threshold below which they simply do not occur.

That threshold is 100 mGy to the fetus.

Above 100 mGy, the risk curve climbs steeply. Below it, deterministic effects are not observed. This isn’t a comfortable regulatory threshold with a safety factor bolted on — it’s based on the actual biology of radiation-induced tissue damage. Below 100 mGy, there are no fetal anomalies, no increase in pregnancy loss. The ACR, ACOG, and the National Council on Radiation Protection all say so explicitly.

Now. What does a trauma CT actually deliver to the fetus?

The RANZCR, in their Diagnostic Radiology and Pregnancy position statement, cites Australian data: CT of the abdomen delivers a mean uterine dose of 7.1 mGy. Range 1–40 mGy. A whole-body trauma CT in a pregnant patient in a French multicentre study delivered a median fetal dose of 38 mGy. A single CT scan — even a full whole-body study — cannot reach 100 mGy.

Not won’t in most cases. Cannot. The ICRP states explicitly that the 100 mGy threshold cannot be reached with a single CT examination.

So the conversation about deterministic effects from a single trauma CT is over. Done. The risk does not exist at diagnostic doses.

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But what about stochastic risk?

Here’s where people get tangled. Stochastic effects — principally childhood leukaemia and solid cancers — have no known safe threshold. Risk increases linearly with dose. There is no floor. And this is where the ALARA principle lives: as low as reasonably achievable, not because diagnostic doses cause deterministic harm, but because we should minimise cumulative stochastic burden where we can do so without compromising the diagnostic objective.

Here’s the important word: where we can.

The background rate of childhood leukaemia is approximately 1 in 3,000. A 10–20 mGy fetal exposure may double that risk. Which means an absolute risk of perhaps 2 in 3,000. An additional 1 in 3,000. In a child who will only exist if their mother survives long enough to deliver them.

ALARA does not mean avoid. ALARA does not mean hesitate when a woman’s spleen is haemorrhaging. ALARA means apply dose reduction techniques, involve your radiographer, document the estimated dose, and have a counselling conversation — after the scan, not instead of it.

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The β-hCG question

Should you check a β-hCG before scanning? Sure, if it’s immediately available and won’t delay anything. It may be useful for counselling. It tells you nothing about whether to image.

A positive β-hCG at four weeks does not lower the CT threshold. A negative β-hCG does not raise it. The clinical question is the same regardless: does this mechanism and these clinical signs warrant cross-sectional imaging? Answer that question using standard trauma criteria, and then scan if indicated. The pregnancy status is relevant to the conversation you have afterward, not the decision you make now.

If the woman is haemodynamically unstable, you don’t have time for the conversation anyway. You have time for the scan.

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So what is the risk of missing an injury if we do not CT?

This is a tricky question to answer. There is not a lot of data on pregnant women specifically. However if we look at the best, most recent Australian data (11) – the numbers are convincing. The risk of an important occult chest or abdominal injury in patients (even those with normal exam and CXR) is high – someting like 20 -25%.

Up to 19% of patients with normal abdominal examinations were later found to have evidence of injury on their CT scan, and significant injuries detected were otherwise clinically occult, including blunt aortic injury. This is corroborated by non-Australian data that nonetheless speaks directly to the clinical argument.

In population-level studies of pregnant women involved in motor-vehicle collision, maternal death occurred in 3.6 per 1,000 women and fetal death or stillbirth in 6.6 per 1,000. These numbers are about 10-20 times higher than the theoretical risk of CT-induced future childhood malignancy.

In blunt trauma patients with normal sensorium and normal physical examination, 15% were found to have an occult chest injury on CT despite a normal chest exam, 35% had occult injuries on chest CT despite a negative chest exam and negative chest X-ray, and 16% had occult abdominal injuries despite a negative abdominal exam. Overall, 25% of patients with normal chest, abdomen, and pelvis examinations had occult injuries detected on CT.

So, keep that in mind when thinking about risk. We are comparing a possible 1:3000 risk of future badness to a 1:4 or 1:5 risk of missing current real badness. Not even close.

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Why not Ultrasound?

Ultrasound is awesome.  No radiation, no risk right?  Unfortunately, even in the best hands ultrasound cannot give us the answers that we need in women suffering traumatic injury.  We know that US is inferior to CT for injuries such as solid organ and visceral bleeding.  However, it is also very insensitive for uterine injury and abruption – which are common (30-40%) of major trauma in the 3rd trimester.  CT actually has a very high pick up rate for uterine injury and placental abruption.  Obviously we do not use CT to diagnose abruption in non-traumatic scenarios as we can use clinical assessment, CTG and US to guide the management.  However, when trauma happens in later pregnancy the risk:benefit ratio is definitely towards CT as it can pick all the other injuries as well as abruption.  So it is a no-brainer really

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The rural reality

I want to be direct about something that doesn’t appear in the guidelines, because guidelines are written for trauma centres with consultant radiologists on call, obstetric teams available, and someone to second-guess you in a collegial way.

In remote practice, you are the protocol.

You are the trauma team, the intensivist, the obstetrician, and the surgeon. There is no second opinion arriving in twenty minutes. The RFDS is on its way and the window for definitive diagnosis is the window you create right now, with the tools you have.

Withholding a CT because of radiation anxiety in that setting doesn’t make you cautious. It makes you blind. An occult solid organ injury, an aortic haematoma, a mesenteric tear — missed because someone was worried about a stochastic risk of 1 in 3,000 in a fetus that may not even implant — is an entirely avoidable tragedy.

The senior emergency physicians in the study above were the ones most likely to scan regardless of gestational age. The hesitancy was concentrated in those without specific training or experience in this area. That’s important information about where the educational gap is.

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A note on shielding

The lead apron on the abdomen of a pregnant trauma patient is well-intentioned and often unhelpful. Most of the fetal dose in trauma CT comes from internal scatter — radiation that has already passed through the maternal body and is bouncing around internally. External shielding does not significantly reduce that scatter. More importantly, some modern CT scanners use automated dose modulation — if the detector senses lead shielding, it may increase tube current to compensate, actually raising the dose.

Shielding is not harmful, and if it reassures the patient and clinician without delaying or compromising the scan, fine. But it is not a mitigation strategy. It’s a ritual comfort.

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The synthesis

The RANZCR position statement says it plainly: most diagnostic radiological procedures pose no substantial risk to the fetus. The ACEM and RANZCR joint imaging guidelines support CT as the investigation of choice in the trauma context. The WA statewide cohort data — from Fiona Stanley and Royal Perth — found that even in trauma populations receiving multiple CTs, the excess cancer signal was modest against the background of trauma mortality itself.

The literature is not ambiguous. The guidelines are not equivocal. The professional bodies are aligned. And the 88.7% of emergency physicians who describe this as challenging are not reflecting on a genuinely difficult evidence question — they are describing a gut reaction that is costing lives.

Scan her.

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Reference List

Australian and New Zealand Sources

1. Royal Australian and New Zealand College of Radiologists. Diagnostic Radiology and Pregnancy — Clinical Radiology Position Statement. Version 2.0. November 2017. [Under review May 2026.] Available: https://www.ranzcr.com/college/document-library/diagnostic-radiology-and-pregnancy-policy (PDF direct link: https://www.ranzcr.com/wp-content/uploads/edocman/professional-documents/policies/Diagnostic%20Radiology%20and%20Pregnancy%20Position%20Statement.pdf)

2. Australasian College for Emergency Medicine (ACEM); Royal Australian and New Zealand College of Radiologists (RANZCR). Guidelines on Diagnostic Imaging. NSW Agency for Clinical Innovation. Available: https://aci.health.nsw.gov.au/__data/assets/pdf_file/0007/273715/ACEM-Guidelines-diagnostic-imaging.pdf

3. Yaw LK, Song S, Ho KM. Dose-related association between radiation exposure from computed tomography (CT) scans during trauma hospitalisations and subsequent risk of developing new-onset cancers: statewide cohort study, Western Australia 2004–2020. Communications Medicine 2026 Jan 5. doi: 10.1038/s43856-025-01354-z PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12881511/ (Fiona Stanley Hospital / Royal Perth Hospital, WA)

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International Guidelines and Position Statements

4. American College of Obstetricians and Gynecologists. Committee Opinion No. 723: Guidelines for Diagnostic Imaging During Pregnancy and Lactation. Obstet Gynecol 2017;130(4):e210–e216. doi: 10.1097/AOG.0000000000002355 PMID: 28937575 Available: https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/10/guidelines-for-diagnostic-imaging-during-pregnancy-and-lactation

5. Qamar SR, Green CR, Ghandehari H, Holmes S, Hurley S, Khumalo Z, Mohammed MF, Ziesmann M, Jain V, Thavanathan R, Berger FH. CETARS/CAR Practice Guideline on Imaging the Pregnant Trauma Patient. Can Assoc Radiol J 2024 Nov;75(4):743–750. doi: 10.1177/08465371241254966 PMID: 38813997 PubMed: https://pubmed.ncbi.nlm.nih.gov/38813997/

6. McCollough CH, Schueler BA, Atwell TD, Braun NN, Regner DM, Brown DL, LeRoy AJ. Radiation exposure and pregnancy: when should we be concerned? RadioGraphics 2007 Jul–Aug;27(4):909–917. doi: 10.1148/rg.274065149 PMID: 17620458 Available: https://pubs.rsna.org/doi/10.1148/rg.274065149

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Epidemiology and Clinical Practice Data

7. Abback PS, Benchetrit A, Delhaye N, Daire JL, James A, Neuschwander A, Boutonnet M, Cook F, Vinour H, Hanouz JL, Cotte J, Pastene B, Jouffroy V, Gauss T; Traumabase Group. Multiple trauma in pregnant women: injury assessment, fetal radiation exposure and mortality. A multicentre observational study. Scand J Trauma Resusc Emerg Med 2023 May 2;31(1):22. doi: 10.1186/s13049-023-01084-y PMID: 37131266 PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10152762/

8. Karaaslan A, Ipekci A, Karaaslan Y. A Flowchart to Guide Emergency Physicians to Order Radiological Imaging in Pregnant Patients: Findings from an Emergency Department Questionnaire. Healthcare 2025 Dec 2;13(23):3138. doi: 10.3390/healthcare13233138 PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12692375/ (Source of the 88.7% hesitancy figure)

9. MacDermott R, Berger FH, Phillips A, Robins JA, O’Keeffe ME, Abu Mughli R, MacLean DB, Liu G, Heipel H, Nathens AB, Qamar SR. Initial Imaging of Pregnant Patients in the Trauma Bay — Discussion and Review of Presentations at a Level-1 Trauma Centre. Diagnostics 2024 Jan 26;14(3):276. doi: 10.3390/diagnostics14030276 PMID: 38337792 PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10855036/

10. Lucas AN, Tay-Lasso E, Zezoff DC, Fierro N, Dhillon NK, Ley EJ, et al. Significant variation in computed tomography imaging of pregnant trauma patients: a retrospective multicenter study. Emerg Radiol 2024;31:69–77. doi: 10.1007/s10140-023-02195-w PMID: 38148383 PMC: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10830714/

11. Salam Findakly, Adil Zia, Helen Kavnoudias, Joseph Mathew, Dinesh Varma, Bruno Di Muzio, Robin Lee, Heather K Moriarty, Tim Joseph, Warren Clements.
The use of whole-body trauma CT should be based on mechanism of injury: A risk analysis of 3920 patients at a tertiary trauma centre, Injury, Volume 54, Issue 7, 2023, 110828,
https://doi.org/10.1016/j.injury.2023.05.059.

Justin also has a great schema for discussing radiation risk with women over at First10EM