CTPA Radiation Pregnancy — FRCA Final MCQ

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ModerateObstetric AnaesthesiaCTPA Radiation PregnancyFRCA Final

A 30-year-old woman (ASA I, 60 kg) at 36 weeks gestation presents with sudden-onset pleuritic chest pain and breathlessness after a long-haul flight. D-dimer is elevated. CTPA is being considered. What is the fetal radiation dose from a CTPA?

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Correct answer: C — Negligible (<0.01 mGy) – well below the threshold for teratogenesis

The fetal radiation dose from CTPA is very low (<0.01-0.1 mGy), far below the threshold for teratogenic effects (100 mGy). CTPA is the investigation of choice for suspected PE in pregnancy when clinical suspicion is high or when initial investigations (CXR, leg Doppler) are non-diagnostic. The RCOG and NICE recommend that CTPA should NOT be withheld in pregnancy when PE is clinically suspected – the risk of untreated PE (maternal mortality 15-30%) far outweighs the negligible radiation risk. V/Q scan is an alternative with slightly higher fetal dose but lower maternal breast dose.

Reference: RCOG – 2015 – GTG 37b VTE in pregnancy; NICE – 2020 – NG158 VTE