Fetal tyhmus size as a predictor of histological chorioamnionitis in preterm premature rupture of membranes.

Objective: To predict histological chorioamnionitis (CA) in the cases of preterm premature rupture of membranes by using fetal thymus transverse and anteroposterior diameters and areal measurements.

Methods: Fifty healthy and 50 patients diagnosed with preterm premature rupture of membranes (PPROM) between 24 and 37 weeks of gestation were included in the study. Fetal thymus measurements were done and repeated on a weekly basis until delivery, Furthermore white blood cell, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels were measured every other day until delivery, too. Following delivery, all patients' placentas were sent to pathology.

Results: Histological CA was detected in 48% of the PPROM patients. There were no patients in either group with clinical CA. Thymus transverse diameter had 91% sensitivity, 81% specificity, 82% PPV, and 91% NPV in predicting histological CA in PPROM patients. No linear relationship was found between thymus anteroposterior diameter measurements and gestational age. Thymus area measurements have sensitivity of 75%, specificity of 81%, PPV of 78%, NPV of78% in determining CA in patients with PPROM.

Conclusion: Both thymus transverse diameter and area measurement are more significant than sedimentation and CRP values in predicting histological CA. Fetal thymus measurements can be used in early diagnosis of infections among high risk patients.