Imaging in pregnancy

M R C O G PA R T 2 · S O S P O C K E T C A R D · K N O W L E D G E A R E A 5 – A N T E N ATA L C A R E

Imaging in Pregnancy Eastwood K-A, Mohan AR. Imaging in pregnancy. TOG 2019;21:255–262. doi:10.1111/tog.12604

1 mGy <50 mGy 1:17,000 BACKGROUND RADIATION, WHOLE ANY-GESTATION EXPOSURE = NEGLIGIBLE FATAL CHILDHOOD CANCER RISK PER MGY IN PREGNANCY FETAL RISK UTERO

DO N' T-M IS S FA C TS

  1. Background fetal radiation over pregnancy ≈ 1 mGy; <50 mGy at any gestation = negligible risk – do not delay indicated imaging

  2. Stochastic effects (cancer): no threshold dose. Deterministic effects (malformation/FGR/microcephaly): threshold- dependent, worst 5–17 weeks

  3. ICRP childhood cancer risk: 1 in 17,000 per mGy in-utero exposure

  4. MRI: no ionising radiation; safe at any gestation if benefit>risk (ACR); avoid gadolinium unless clearly justified – Ray et al. found ↑stillbirth/neonatal death (adjusted RR 3.70) with gadolinium exposure

  5. Iodine-131 crosses placenta, half-life 8 days, risk of fetal hypothyroidism >10–12 weeks – avoid; use technetium-99m instead

  6. Suspected PE: CTPA (up to 20 mGy maternal breast dose) vs V/Q (higher fetal dose, lower breast dose) – choose V/Q if breast cancer history

  7. DVT: compression duplex ultrasound first-line; if negative but suspicion high, repeat on days 3 and 7

  8. Breast mass >2 weeks → MDT referral; ultrasound + biopsy first, mammography if malignant (sensitivity 78–90%)

MODALITY QUICK-PICK

Ultrasound/MRI (no contrast): first-line, abdo pain, headache work-up Avoid: gadolinium (unless essential), iodine-131

ABBREVIATION KEY

ALARA — as low as reasonably achievable MRA/MRV — magnetic resonance angiogram/venogram

CT — computed tomography MRI — magnetic resonance imaging

CTPA — CT pulmonary angiogram PET — positron emission tomography

CTV — CT venogram PRES — posterior reversible encephalopathy syndrome

DVT — deep venous thrombosis RR/HR — relative risk/hazard ratio

FDG — 2-deoxy-2[fluorine-18]-fluoro-D-glucose Sv/mSv — sievert/millisievert (effective dose)

Gy/mGy — gray/milligray (absorbed dose) SSFSE — single-shot fast spin echo

ICRP — International Commission on Radiological Protection VTE — venous thromboembolism

IQ — intelligence quotient V/Q — ventilation/perfusion scan

Source: The Obstetrician & Gynaecologist (TOG), RCOG journal — Eastwood K-A, Mohan AR. Imaging in pregnancy. TOG 2019;21:255–262. doi:10.1111/tog.12604

Clinically reviewed by NHS obstetricians and gynaecologists

MRCOG AI is an independent educational tool. It is not affiliated with, endorsed by, or connected to the Royal College of Obstetricians and Gynaecologists (RCOG).

Included with a Pass Package

Start free