Nomograms of the fetal thymus for clinical practice

Abstract

Introduction: The fetal thymus may be visualized using ultrasonography (USG) and is typically located in the mediastinum. In the past years, the size of the fetal thymus has served not only as a marker of genetic or heart defects but also as a predictive factor for intrauterine growth restriction, premature birth, preeclampsia, chorioamnionitis or even neonatal sepsis. Material and methods: A total of 410 fetuses were qualified for the study. Fetuses with heart defects were excluded from the study. The fetal thymus was evaluated with ultrasonography between the 14 th and 40 th week of gestation. After obtaining a standard transverse view encompassing the three great vessels, thymus measurements were attempted, i.e. maximal transverse diameter, circumference and surface area. Linear regression was used for statistical analysis, yielding 3 models, each with a different dependent variable. The confidence interval for each model was set at 80% to aid the comparison with centile grid growth charts for neonates and children. The test was regarded as statistically significant when p < 0.05. Results: From a total of 410 fetuses the thymus transverse diameter, circumference and area were successfully measured in 410, 320 and 330 cases, respectively. The probabilities are lower than 0.0005 for each model, which means that each model is quite statistically significant. Conclusions: The coverage of healthy thymus nomograms in the fetal population may be the basis for the identification of fetuses at risk of hypoplasia or thymic hyperplasia, which seems particularly important from the point of view of the detection of potential inborn immunological disorders

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

“…At the end of the perinatal period and immediately after birth the thymus is large in size. By the age of adolescence, it slowly begins to atrophy, however not entirely [1]. Thymus development is critical for the establishment of a normal immune system in a foetus, neonate and toddler.…”

“…It is the easiest method, reproducible and available for examination even in advanced pregnancy. The obtained measurements were juxtaposed with nomograms for thymus size in healthy foetuses whose mothers had no history of diabetes (the nomograms from 410 foetuses were designed and published by the team of ultrasound and echocardiography experts from the Department of Prenatal Cardiology at the Polish Mother's Memorial Research Institute in Lodz) [1]. Prior to ultrasound examination the participants were asked to complete a questionnaire regarding their body weight status before 10 weeks of gestational age, which allowed us to assess the baseline BMI 9 .…”

Placental thickness in the 2D prenatal ultrasonographic examination

“…There are parameters that indicate a much clearer correlation between themselves and GA comparing with PTh – for example: abdominal circumference, transversal diameter of the foetal heart, or thymus circumference [ 24 – 26 ]. Papers regarding the correlation between PTh and GA in the ultrasound examination present varied data, but they all agree that there is a positive correlation.…”

Fetal thymus in growth-restricted fetuses due to placental insufficiency

“…This process is also reported in chorioamnionitis and fetal inflammatory response syndrome, and recently, it has been investigated in preeclampsia, maternal diabetes, and COVID-19 infection [4][5][6][7][8] . Small thymus is associated with an increased child mortality, and its postnatal evaluation can predict the likelihood of survival in preterm infants 9,10 .…”