Two- and Three-Dimensional Ultrasonographic Evaluation of the Fetal Thymus in Women with Preterm PrematureRupture of Membranes: A Prospective Study

Abstract

Objective: To evaluate the relationship between fetal thymus diameter and perinatal outcomes in preterm premature rupture of membranes (PPROM) cases and to compare three-dimensional (3D) fetal thymus volume in the same cases. Material and Methods: This was a prospective study from March 2019 through March 2020. Women diagnosed with PPROM between 24 and 33+6 weeks of gestation were included. Pregnancies were divided into 2 groups as small and normal according to the thymus size nomogram. The virtual organ computeraided analysis software calculated the volumes automatically. Results: In 41 patients, measurements could be successfully acquired with twodimensional and 3D sonography. Twenty eight (68.3%) patients were in the small thymus group and 13 patients (31.7%) were in the normal thymus group. The probability of clinical chorioamnionitis increased 7.7-fold-times in cases with small thymus (odds ratio 7.7, 95% confidence interval 1.1-67.4, p=0.038). The latency period was significantly higher in the normal thymus group. The correlation between transverse diameter and thymus volume was analyzed according to gestational age at ultrasound measurement and a significant correlation was observed between them. Conclusion: A small transverse diameter of the thymus in PPROM cases may be associated with clinical chorioamnionitis, and a normal thymus diameter may predict a longer latency period. In addition, although transverse thymus diameter was correlated with thymus volume, no significant volume difference was observed between the groups when percentile classification was made.