Purpose: To sonographically evaluate the thymic size in preterm infants.
Material and methods: In 6 healthy infants, born in gestational weeks 34-37, and 6 infants born in weeks 24-32, the thymic volume estimate (the thymic index) was assessed. The measurements were compared to the estimates calculated from the prediction model for neonates.
Results: The slightly preterm infants fit the prediction model. In cases where the results failed to fit into the model, it was adjusted in order to cover lower birth rates. The extremely preterm infants initially had a very low thymic index but, when healthy, they reached the normal range.
Conclusion: With the knowledge of the birth weight it is now possible to predict the thymic size in healthy infants weighing 2,070 g or more.