Measuring fetal thymus size: a new method for diabetes screening in pregnancy.

To investigate the correlation between fetal thymus size and diabetes in pregnancy. Fetal thymus size was assessed in 160 pregnant women with gestational age of 19-39 weeks. They included 80 diabetic (investigation group) and 80 nondiabetic (control group) women. Fetal thymus size was measured by thymic-thoracic ratio. We did this with dividing the thymus' anteroposterior diameter by anteroposterior of mediastinum. Thymic-thoracic ratio was significantly smaller in fetuses of diabetic mothers compared to the nondiabetic group ( = .001). It remained significant after subgrouping diabetic mothers into overt diabetes, insulin-dependent gestational diabetes, and noninsulin-dependent gestational diabetes. Although thymus size was smaller in fetuses of diabetic pregnant women compared to nondiabetic pregnant women, it seems that thymic-thoracic ratio can be a predictor of diabetes and its other related adverse effects during pregnancy.