EP10.12: Sonographic evaluation of the fetal thymus using the thy-box technique between 18 and 22 weeks' gestation in a multicentric study

To assess the feasibility of fetal thymus measurement between 18 and 22 weeks' gestation, using the thy-box technique. A multicentric cross-sectional study was performed on pregnant women (singleton and twin pregnancies) attending for routine US exam 7 centres in Spain (15 examiners). The fetal thymus was shown in an axial plane of the upper mediastinum. Colour Doppler imaging was applied to outline the thy-box: i.e. the area between the brachiocephalic artery posteriorly and internal mammary arteries laterally. Measurements of the lateral and anteroposterior diameters of the thymus were performed. Maternal, fetal, and ultrasound factors affecting feasibility were analysed. A total of 1505 cases were assessed. The Thy-box was feasible in 88.6% of the cases. The mean anteroposterior thymus diameter was 6.11 ± SD 1.67 mm and the mean transverse diameter was 11.48 ± SD 2.86 mm. Non-feasible cases were significantly related to maternal body index, breech presentation, fetal occipito-anterior position, twin pregnancy and exploration time. Examiner does not affect the feasibility buy may affect the measurement providing greater variability (figure 1). Supporting information can be found in the online version of this abstract Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.