Association Between Fetal Thymus Size and Intrauterine Growth Restriction

Objective: The objective of this study was to evaluate the association between reduced fetal thymus size and intrauterine growth restriction (IUGR). This study was devised to determine the association between thymus size and any abnormal Doppler indices within the fetal umbilical artery (UA), as well as the middle cerebral artery (MCA). Materials and Methods: Forty-six pregnancies between 20 and 38 weeks of gestation with IUGR and 46 normal pregnancies within similar gestational age (GA) range were included. The transverse diameter of fetal thymus was measured. In the IUGR group, the fetal umbilical artery (UA) and middle cerebral artery (MCA) Doppler flow velocities were recorded. Results: The mean GA of fetuses with IUGR (33.5 weeks) was higher than control group (30.3 weeks). To adjust for the effect of GA, analysis of covariance (ANCOVA) was performed. The adjusted mean thymus diameters were 19.02 mm in IUGR and 21.25 within the control group (mean difference = 2.23 mm; P = .02). The mean (±SD) thymus size in 16 fetuses, with abnormal Doppler findings, was significantly lower than in the group with normal Doppler findings, 17.45 (±2.50) vs 22.02 (±5.39) mm; P < .001. Conclusion: IUGR may be associated with reduced fetal thymus size, especially when coupled with abnormal Doppler findings. The thymus size in a group of IUGR fetuses, with abnormal Doppler findings, was smaller than IUGR fetuses, with normal Doppler findings.

Influence of Covid-19 infection on fetal thymus size after recovery

Objectives To investigate the long-term effects of the SARS-CoV-2 infection on the fetal immune system by fetal thymus size measurements with ultrasound (USG). Methods This prospective study was conducted in the Turkish Ministry of Health Ankara City Hospital between November 1, 2020 and April 1, 2021, with recovered, pregnant women, four weeks after they had been confirmed for the SARS-CoV-2 infection by real-time polymerase-chain-reaction (RT-PCR). COVID-19 recovered (CR) pregnant women compared with age-matched pregnant controls in terms of demographic features, fetal thymic-thoracic ratio (TTR), and laboratory parameters. Results There was no difference in demographic features between the two groups. TTR found significantly lower in the CR group than the control group (p=0.001). The fetal TTR showed a significant and moderate correlation with maternal monocyte counts, monocyte to lymphocyte ratio (MLR), and red cell distribution width (RDW); while it did not correlate with lymphocyte counts, c-reactive protein (CRP), and procalcitonin levels. Conclusions The 2019 novel coronavirus disease (COVID-19) reduces fetal thymus size in pregnant women with mild or moderate symptoms after recovery from the infection.

Second trimester fetal thymus size in association to preterm birth

Objectives The aim of this study was to compare the second trimester thymus-thorax-ratio (TTR) between fetuses born preterm (study group) and those born after 37 weeks of gestation were completed (control group). Methods This study was conducted as a retrospective evaluation of the ultrasound images of 492 fetuses in the three vessel view. The TTR was defined as the quotient of a.p. thymus diameter and a.p. thoracic diameter. Results Fetuses that were preterm showed larger TTR (p<0.001) the second trimester than those born after 37 weeks of gestation were completed. The sensitivity of a binary classifier based on TTR for predicting preterm birth (PTB) was 0.792 and the specificity 0.552. Conclusions In our study, fetuses affected by PTB showed enlarged thymus size. These findings led us to hypothesize, that inflammation and immunomodulatory processes are altered early in pregnancies affected by PTB. However, TTR alone is not able to predict PTB.

Diagnostic Value of Fetal Thymus Size in Intrauterine Growth Restriction

Background: Changes in thymus size and histopathology have been observed both in animal models of intrauterine growth restriction (IUGR). The aim of the present study was to evaluate the size of the fetal thymus by sonography in pregnancies with IUGR and to search for a possible relationship between a fetal thymus size and adverse perinatal outcomes. Methods: This prospective observational study was carried out on 100 participants who were divided into two groups. Group A: Study group which include 50 patients with IUGR. Group B: Control group which Include 50 normal patients with appropriate gestational age. All patients were subjected to: History taking: (Personal, Obstetric History, Maternal Medical History) and trans-abdominal ultrasound. Results: IUGR group show statistically significant decrease in the estimate of fetal weight (EFW) compared to the control group (P<0.05). Doppler study of umbilical artery shows significant increase of (pulsatility index (PI), resistance index (RI) and systolic/diastolic (S/D) in IUGR group when compared to control group. Doppler study of middle cerebral artery (MCA) shows significant increase in (RI, SD) in IUGR group when compared to control group while PI doesn’t show significant difference between two groups. Thymus size decrease in IUGR group when compared to the control group. IUGR group had low survival and lower APGR Score when compared to the control group. Correlation between thymus size with the studied doppler parameters and pregnancy outcome in the current study. Umbilical Doppler RI, PI and SD showed statistically significance in this study (P<0.05) and this means that the blood flow in the umbilical arterial (UA) is important for the fetus. As regard the MCA RI and SD Doppler, they show statistically significance in this study (P<0.05) while the MCA PI Doppler did not show any statistically significance in this study (P>0.05). Conclusions: IUGR is associated with small thymus and small fetal thymus may be an early indicator of adverse perinatal outcomes in pregnancies complicated by IUGR.

Human CD34+ cell isolation from fetal liver, and fetal thymus preparation v1

This protocol details the steps for isolating human CD34+ cells from human fetal liver. It also explains how to prepare human fetal thymus for immediate use or for freezing, as well as the process for thawing. The CD34+ cells are hematopoietic progenitor cells and can be used to generate humanized mice through reconstitution of immune cells via IV injection after bone marrow ablation. These cells can also be used for mixed lymphocyte reaction experiments.

A General Guide To Generate Different Humanized Mouse Models v1

This protocol details how to create humanized mouse models from NSG mice. Four different variants of humanized mice can be generated based on whether or not the native thymus is retained or if a human thymus piece is transplanted. Which type of humanized mouse is desired depends on the goals for the experiment. See our protocols on NSG mouse thymectomy, human CD34+ cell isolation, and human fetal thymus preparation for more details on some of the steps in this protocol (“Thymectomy procedure to remove native thymus of NSG mice”, “Human CD34+ cell isolation from fetal liver, and fetal thymus preparation”, “CD34+ isolation from human bone marrow”).