Can diabetes influence fetal thymus size during pregnancy?

The aim of the study was to evaluate fetal thymus size by sonography in diabetic pregnancies and its relationship with diabetes type.

In this prospectively designed case-control study, fetal thymus transverse diameter and circumference of the fetal thymus were measured. Also, TTR (thymic-thoracic ratio) was assessed in 288 healthy and 105 diabetic pregnancies. Patients were divided into subgroups as diet-controlled gestational diabetes (GDMA1, n = 40), insulin-dependent (GDMA2, n = 42), and pregestational diabetes mellitus (PGDM, n = 23). GDM was diagnosed between 24 and 28 weeks of gestation with a 75 g oral glucose tolerance test. Measurements were compared to the healthy control group. Pairwise comparisons with Bonferroni correction determined which type of diabetes was independently associated with a small fetal thymus.

All 3 maternal diabetes categories had smaller fetal thymus size than controls (p < 0.05). TTR were lowest in PGDM (p < 0.05).

Gestational diabetes is associated with smaller fetal thymus size. Pregestational diabetes may be associated with a smaller fetal thymus compared to diet-controlled GDM. Also, the thymus size may be even smaller in those with poor blood glucose regulation.