PE Imaging in Pregnancy — EECC MCQ

Correct answer: C — V/Q scan is generally preferred over CTPA in pregnancy — it delivers a lower radiation dose to maternal breast tissue (~0.5 mGy vs ~10-20 mGy for CTPA), and the fetal dose is comparable for both; however, CTPA is preferred if the CXR is abnormal

PE imaging in pregnancy is a nuanced decision. The ESC 2019 PE Guidelines and RCOG guidelines recommend: (1) V/Q scan as first-line if CXR is normal (lower maternal breast radiation dose — important for breast cancer risk in young women; fetal radiation dose is comparable ~0.1-0.5 mGy for both); (2) CTPA if CXR is abnormal (V/Q is less interpretable with lung pathology); (3) CTPA if V/Q is indeterminate. Key considerations: (1) D-dimer is physiologically elevated in pregnancy (sensitivity maintained but specificity markedly reduced — pregnancy-specific thresholds or clinical probability-adjusted approaches are used); (2) withholding imaging due to radiation concerns is DANGEROUS — untreated PE has a 30% mortality vs negligible radiation risk from either modality; (3) bilateral leg compression ultrasound may be performed first — if positive for DVT, PE is treated without lung imaging.

Reference: ESC (2019): PE Guidelines; RCOG Green-top Guideline