Assessment of fetal thymus size and BMI in pregnant women with diabetes

Objectives: The purpose of this study is to demonstrate whether diabetes during pregnancy affects the development of the fetal immune system. The background: evaluation of potential complications in diabetic pregnancy. The objective is evaluation of the significance of a new ultrasound method of thymus size in pregnancies complicated by diabetes. Material and methods: The analysis was performed with the use of IBM SPSS Statistics 25.0 software. The Mann– –Whitney U test was used for comparison of two groups, i.e., diabetic pregnancies and non-diabetic pregnancies, whereas Kruskal–Wallis H test was used to compare multiple groups. A linear regression model was used to determine the correlation between the type of diabetes and fetal thymus size as well as between maternal body mass index (BMI) and fetal thymus size. The significance level α was set at 0.05. Results: A comparison between diabetic and non-diabetic pregnancies was made with the use of Kruskal–Wallis H test. The compared groups included women without gestational diabetes, with pre-gestational diabetes, gestational diabetes managed by diet and gestational diabetes treated with insulin and diet. The analysis revealed significant differences between the compared groups, H (3) = 23.06; p < 0.001; ƞ2 = 0.04. The additional post hoc Dunn’s test with Bonferroni correction of the significance level was used to explore specific differences between group means. The results of this detailed analysis indicated that foetuses of diabetic mothers treated with diet had smaller thymus than foetuses of non-diabetic mothers (p = 0.001). Linear regression analysis was used to establish whether maternal BMI (defined as the body mass divided by the square of the body height and expressed in units of kg/m²) affects fetal thymus size. The analysis found no correlation between maternal BMI divided into the following categories: 18.5–24.99 normal weight, 25–29.99 overweight, 30.00–34.99 obese class I, 35.00– 39.99 obese class II and ≥ 40.00 very severely obese, and fetal thymus size, b = −1.82; SE = 2.17; t = −0.84; p = 0.405; R² < 0.01. Conclusions: Thymus size is statistically smaller in foetuses of diabetic mothers when compared to healthy controls.