Ultrasonographic evaluation of fetal thymus size in normal and in diabetic pregnant women

Background In the 12 week of gestation, the thymus moves to its ventral location, which is between the aortic arch and the bottom of the heart. Aim This study aimed to compare the fetal thymus diameters of two groups of pregnant women: one with gestational diabetes mellitus (GDM) and another without the condition, using ultrasonography as the method of measurement. There was also an attempt to establish a correlation between maternal blood glucose levels and the size of the fetal thymus. Patients and methods This case-control study included 110 pregnant women, aged from 20 to 35 years, who were experiencing singleton pregnancies from 24 to 28 weeks of gestation. The participants were separated into two groups of equal size. The study group consisted of pregnant women diagnosed with GDM, whereas the control group included healthy pregnant women. Results The study group had considerably decreased thymus diameter and TT ratio compared with the control group ( P <0.001). A substantial negative association exists between fetal thymus size and maternal blood glucose levels (r= –0.253, P =0.007) and postprandial blood glucose (r= –0.565, P <0.001). Fetal thymus diameter predicts GDM (area under the curve=0.856, P <0.001) with 80% sensitivity and 74.55% specificity. TT ratio predicts GDM with 78.18% sensitivity and 67.27% specificity (area under the curve=0.836, P <0.001). Fasting and postprandial blood glucose levels were considerably higher in the study group compared with the control group ( P <0.001). Conclusions Fetal thymus size measured ultrasonographically may serve as a potential indicator for the presence of GDM.