Evaluation of fetal thymus size in maternal autoimmune diseases: systemic lupus erythematosus, Sjögren’s syndrome and antiphospholipid antibody syndrome

PURPOSE: To investigate the effect of inflammation on the fetal thymus-thoracic ratio (TTR) in pregnant women with systemic lupus erythematosus (SLE), Sjögren’s syndrome (SS) and antiphospholipid antibody syndrome (APS). METHOD: This prospective case–control study included 45 pregnant women with SLE, SS, and APS and 90 gestational age-matched healthy pregnant women between 24 and 37 gestational weeks. The ratio of the anteroposterior fetal thymus length to the transverse mediastinal length was calculated as the TTR in the study groups. RESULTS: Fetal TTR was significantly lower in the case group (p < 0.001). Fetal TTR in the APS group was significantly lower than SS group (p = 006). The patients using hydroxychloroquine (HCQ) had significantly higher fetal TTR compared to patients not using HCQ (p = 0.004). A moderate negative correlation was found between the disease duration and fetal TTR (r = − 0.552, p < 0.001). In predicting admission to the neonatal intensive unit care (NICU), a value of 0.31 was found for the fetal TTR with a sensitivity of 83.3% and a specificity of 69% CONCLUSION: Maternal inflammation in pregnancies with autoimmune diseases may affect the intrauterine milieu of the fetus and cause a lower fetal TTR. Additionally, the lower level of fetal TTR may be more effective and beneficial for the clinician if combined with other risk factors in predicting NICU admission.