Objective: Children with Down syndrome (DS) can have hypoplastic thymuses with an impaired capacity to liberate newly generated T cells. We sought to determine if the size of the thymus in DS fetuses is different from control fetuses.
Methods: We performed comprehensive prenatal sonographic evaluation that included measurements of the thymus in 874 control fetuses and in 12 DS fetuses. We used graphic comparisons between thymic measurements obtained from the two groups of fetuses and a nested case-control validation study in which DS fetuses were matched for gestational age with control fetuses using a 2-to-1 ratio to make group comparisons.
Results: The plot analysis showed that more than two-thirds of DS fetuses had sonographic signs of thymic hypoplasia. The nested case-control study confirmed that the thymus of DS fetuses was statistically smaller than the thymus of control fetuses [DS transverse diameter 12.3 mm, interquartile range (IQR) 6.2 vs. control 18.1 mm, IQR 4.4; p < 0.001 and, DS perimeter 30.9 mm, IQR 20.1 vs. control 48.6 mm, IQR 20.4; p < 0.01].
Conclusions: Our findings suggest that the majority of DS fetuses have smaller thymuses than control. Prenatal measurements of the thymus may be clinically useful in the management of DS pregnancies.
Copyright © 2011 John Wiley & Sons, Ltd.