Prognostic Value of Fetal Thymus Size in Intrauterine Growth Restriction

Assessment of the fetal thymic-thoracic ratio in pregnant women with intrahepatic cholestasis: a prospective case-control study

OBJECTIVES

To examine the fetal thymic-thoracic ratio (TTR) in intrahepatic cholestasis of pregnancy (ICP).

METHODS

This prospective case-control study was conducted in a single tertiary center. The sample consisted of 86 pregnant women at 28-37 weeks of gestation, including 43 women with ICP and 43 healthy controls. TTR was calculated for each patient using the anterior-posterior measurements of the thymus and intrathoracic mediastinal measurements.

RESULTS

The median TTR value was found to be smaller in the ICP group compared to the control group (0.32 vs. 0.36, p<0.001). The ICP group had a greater rate of admission to the neonatal intensive care unit (NICU) (p<0.001). Univariate regression analysis revealed that lower TTR values increased the possibility of NICU admission six times (95 % confidence interval: 0.26-0.39, p=0.01). A statistically significant negative correlation was detected between TTR and the NICU requirement (r: -0.435, p=0.004). As a result of the receiver operating characteristic analysis, in predicting NICU admission, the optimal cut-off value of TTR was determined to be 0.31 with 78 % sensitivity and 67 % specificity (area under the curve=0.819; p<0.001).

CONCLUSIONS

We determined that the fetal TTR may be affected by the inflammatory process caused by the maternal-fetal immune system and increased serum bile acid levels in fetal organs in the presence of ICP. We consider that TTR can be used to predict adverse pregnancy outcomes in patients with ICP.

Fetal Thymus Size at 19-22 Weeks of Gestation: A Possible Marker for the Prediction of Low Birth Weight?

INTRODUCTION

The purpose was to compare thymus size measured during second trimester screening of fetuses who were subsequently small for gestational age at birth (weight below 10th percentile, SGA group) with fetuses with normal birth weight (control group). We hypothesized that measuring the fetal thymic-thoracic ratio (TT-ratio) might help predict low birth weight.

METHODS

Using three-vessel view echocardiograms from our archives, we measured the anteroposterior thymus size and the intrathoracic mediastinal diameter to derive TT-ratios in the SGA (n = 105) and control groups (n = 533) between 19+0 and 21+6 weeks of gestation. We analyzed the association between TT-ratio and SGA adjusted to the week of gestation using logistic regression. Finally, we determined the possible TT-ratio cut-off point for discrimination between SGA and control groups by means of receiver operating characteristics (ROC) curve analysis.

RESULTS

The TT-ratio was significantly higher in the SGA group than in the control group (p < 0.001). An increase of the TT-ratio by 0.1 was associated with a 3.1-fold increase in the odds of diagnosing SGA. We determined that a possible discrimination cut-off point between SGA and healthy controls was achieved using a TT-ratio of 0.390 (area under the ROC curve 0.695).

CONCLUSION

An increased TT-ratio may represent an additional prenatal screening parameter that improves the prediction of birth weight below the 10th percentile. Prospective studies are now needed to evaluate the use of fetal thymus size as predictive parameter for adverse fetal outcome.

Changes in the thymus gland with age: A sonographic evaluation

Background

Ultrasound evaluation of normal, ectopic, asymmetric, and hyperplastic thymus and also its differentiation from abnormalities are challenging in children, and few studies have addressed this issue. This study aimed to investigate the thymus sonographic changes with age.

Methods

In this cross-sectional study, 118 healthy children were categorised into six age groups. Sonographic features of the thymus, including volume, anatomical position, symmetry, and echo-texture, were recorded.

Results

The thymus was visible at all ages from the suprasternal view. In 77.5% of participants, the thymus gland volume in lobes was symmetrical; however, left (21.2%) and right (1.3%) predominance were also found. The most common position of the thymus was in front of the great vessels (100%) with suprasternal extension (97.5%). The mean volume of thymus was 21.3 ± 10.5 (mm). There was no significant difference in the volumes of the thymus between different age groups. The predominant echo-texture of the thymus in different age groups was hypoechoic with thin echogenic septa (liver-like) in below 2-3 years of age, the appearance of echogenic foci and hyperechoic echo-texture (liver-like with starry sky) in 2-14 years, and uniform hyperechoic echo-texture (fatty liver-like) or geographic echo-texture with coarse reticular pattern in above 14 years.

Conclusion

In children, the thymus gland is visible in ultrasound examination in all age groups from the suprasternal view; however, the echo-texture of the normal thymus changes with age. There was no significant correlation between age and sex with total thymic volume. The specificity of these appearances has made ultrasound a problem-solving modality in children.

Prenatal Sonographic Three-dimensional Virtual Organ Computer-assisted Analysis Thymic Volume Calculation May Predict Intrauterine Growth Restriction

Background

Intrauterine growth restriction (IUGR) refers to fetuses that are small for their gestational age. There is no effective test to predict this disease. The aim of our study is whether fetal three-dimensional (3D) ultrasonography (USG)-assisted thymus volume (TV) measurement predicts IUGR cases.

Methods

Fetal 3D USG thymus measurement between 15 and 24 weeks of gestation was performed in a total of 100 women of reproductive age. Fetal TV was measured using the virtual organ computer-assisted analysis system program. All cases were followed up in terms of pregnancy complications until delivery.

Results

IUGR was developed in six cases in total. In cases with IUGR, mean fetal TV was found to be statistically significantly lower than in healthy cases without it. When the fetal TV was taken as 0.1645, the sensitivity was calculated as 89.5% and the specificity as 50% for predicting IUGR. The use of low fetal volume parameters is a significant and good indicator for predicting IUGR according to the binary logistic regression analysis result.

Conclusion

According to the results of this study, 3D fetal TV measurement may be used in routine second-trimester sonographic anomaly screening to predict the development of fetal IUGR. In this way, fetal mortality and morbidity caused by IUGR may be reduced.

Fetal thymus in growth-restricted fetuses due to placental insufficiency

OBJECTIVE

The aim of this study was to assess fetal thymus size by ultrasound in growth-restricted fetuses due to placental insufficiency and compare to high-risk and low-risk pregnancy fetuses with normal placental function.

METHODS

This is a nested case-control study of pregnant women followed up at a university hospital (July 2012 to July 2013). In all, 30 pregnant women presenting small fetuses for gestational age (estimated fetal weight <p10) due to placental insufficiency (umbilical artery Doppler >p95) were compared to 30 high-risk and 30 low-risk pregnancies presenting normal Doppler indices. The thymus transverse diameter and perimeter were converted into zeta score according to the normal values for gestational age. Head circumference and femur length were used to calculate ratios.

RESULTS

Fetal thymus were significantly lower in pregnancies with placental insufficiency when compared to high-risk and low-risk pregnancies presenting, respectively, transverse diameter zeta score (-0.69±0.83 vs. 0.49±1.13 vs. 0.83±0.85, p<0.001) and P zeta score (-0.73±0.68 vs. 0.45±0.96 vs. 0.26±0.89, p<0.001). There was also a significant difference (p<0.05) in the ratios among the groups: pregnancies with placental insufficiency (TD/HC=0.10, P/FL=1.32, and P/HC=0.26), high-risk pregnancies (TD/HC=0.11, P/FL=1.40, and P/HC=0.30), and control group (DT/HC=0.11, P/FL=1.45, and P/HC=0.31).

CONCLUSION

Fetal thymus size is reduced in growth-restricted fetuses due to placental insufficiency, suggesting fetal response as a consequence of the adverse environment.

Finding the best method for screening for gestational diabetes mellitus: fetal thymic-thoracic ratio or fetal thymus transverse diameter

OBJECTIVE

The aim of this study was to compare the efficiency of fetal thymic-thoracic ratio and fetal thymus transverse diameter measurements in gestational diabetes mellitus.

METHODS

Fetal thymic-thoracic ratio and fetal thymus transverse diameter were assessed in 360 pregnant women. Patients were examined in two groups: 180 gestational diabetes mellitus (study group) and 180 healthy pregnant women (control group).

RESULTS

There were no statistically significant differences between the cases with gestational diabetes mellitus and the control group in terms of fetal thymus transverse diameter; however, the fetal thymic-thoracic ratio was found to be significantly lower in cases with gestational diabetes mellitus compared to that in the control group (p<0.001).

CONCLUSION

The fetal thymic-thoracic ratio is superior to the fetal thymus transverse diameter in evaluating the fetal thymus size.

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.

Effects of intrauterine growth restriction during late pregnancy on the cell growth, proliferation, and differentiation in ovine fetal thymuses

Objective

This study investigated the effects of intrauterine growth restriction (IUGR) during late pregnancy on the cell growth, proliferation, and differentiation in ovine fetal thymuses.

Methods

Eighteen time-mated Mongolian ewes with singleton fetuses were allocated to three groups at d 90 of pregnancy: restricted group 1 (RG1, 0.18 MJ ME/body weight [BW]^0.75/d, n = 6), restricted group 2 (RG2, 0.33 MJ ME/BW^0.75/d, n = 6) and control group (CG, ad libitum, 0.67 MJ ME/BW^0.75/d, n = 6). Fetuses were recovered at slaughter on d 140.

Results

The G0/G1 phase cell number in fetal thymus of the RG1 group was increased but the proliferation index and the expression of proliferating cell nuclear antigen (PCNA) were reduced compared with the CG group (p<0.05). Fetuses in the RG1 group exhibited decreased growth hormone receptor (GHR), insulin-like growth factor 2 receptor (IGF-2R), and their mRNA expressions (p<0.05). For the RG2 fetuses, there were no differences in the proliferation index and PCNA expression (p>0.05), but growth hormone (GH) and the mRNA expression of GHR were lower than those of the CG group (p<0.05). The thymic mRNA expressions of cyclin-dependent protein kinases (CDKs including CDK1, CDK2, and CDK4), CCNE, E2-factors (E2F1, E2F2, and E2F5) were reduced in the RG1 and RG2 groups (p<0.05), and decreased mRNA expressions of E2F4, CCNA, CCNB, and CCND were occurred in the RG1 fetuses (p<0.05). The decreased E-cadherin (E-cad) as a marker for epithelial-mesenchymal transition (EMT) was found in the RG1 and RG2 groups (p< 0.05), but the OB-cadherin which is a marker for activated fibroblasts was increased in fetal thymus of the RG1 group (p<0.05).

Conclusion

These results indicate that weakened GH/IGF signaling system repressed the cell cycle progression in G0/G1 phase in IUGR fetal thymus, but the switch from reduced E-cad to increased OB-cadherin suggests that transdifferentiation process of EMT associated with fibrogenesis was strengthened. The impaired cell growth, retarded proliferation and modified differentiation were responsible for impaired maturation of IUGR fetal thymus.

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.

Relationship between birth weight or fetal growth rate and postnatal allergy: A systematic review

BACKGROUND

Individual susceptibility to allergic diseases is developmentally programmed by early-life exposures. Evidence from preclinical studies suggests that intrauterine growth restriction is protective against later inflammatory responses to allergens.

OBJECTIVE

We sought to evaluate whether prenatal growth affects susceptibility to allergy in human subjects.

METHODS

We systematically searched for relevant studies in 11 databases, including Web of Science, ProQuest, EMBASE, and PubMed. We included only studies that corrected for gestational age or were restricted to full-term infants to separate effects of fetal growth from those of prematurity.

RESULTS

The 42 eligible studies included prospective and retrospective cohort, cross-sectional, and case-control studies. Only 2 studies reported allergic asthma. A birth weight increase of 1 kg was associated with a 44% greater risk of food allergy in children (odds ratio [OR], 1.44; 95% CI, 1.04-1.99; P = .001), a 17% greater risk of ever allergic dermatitis in children (OR, 1.17; 95% CI, 1.04-1.32; P = .008), and a 34% greater risk of ever or current allergic dermatitis in infants up to 2 years of age (OR, 1.34; 95% CI, 1.08-1.68; P = .009). Risks of allergic rhinitis were not associated with birth weight.

CONCLUSIONS

The results of these meta-analyses suggest that intrauterine growth restriction protects against allergic diseases in human subjects consistent with preclinical evidence but that effects might differ between allergic diseases. The strongest evidence is available for infancy and early childhood, and additional studies in older children and adults are needed to determine whether the effects of prenatal growth on each allergic disease persist or differ between those with severe and mild phenotypes.

Growth Restriction and Systemic Immune Development in Preterm Piglets

Background: Many preterm infants are born with growth restriction (GR) following maternal or fetal complications before birth. Such infants may continue to grow slowly after birth, regardless of birth weight (BW), due to morbidities related to their immature organs. Severe GR increases the susceptibility to infections, but it is not clear if this is a consequence of impaired systemic immunity or other factors, such as prolonged hospital stay or poor mucosal barrier function. Using preterm pigs as models for preterm infants, we hypothesized that moderate GR, exerting limited clinical effects, does not influence systemic immune development.

Methods: Preterm pigs were delivered by cesarean section and fed bovine milk diets until 19 d. Piglets with fetal growth restriction (F-GR, the lowest 25% of BW, n = 27, excluding those with BW <350 g) and postnatal growth restriction (P-GR, the lowest 25% of postnatal growth rate, n = 24) were compared with their corresponding controls (F-CON, n = 92, and P-CON, n = 85, respectively). Organ weights were determined and blood collected for assessment of clinical status (blood chemistry and hematology). For a subgroup (n = 58), in depth analyses of neutrophil function, T cell counts, plasma cytokine levels, and leucocyte gene expression were performed.

Results: For F-GR pigs, adrenal gland weight was increased and bone mineral content decreased at 19 d. Total leucocyte levels were lower at birth and interleukin-10 levels increased at d 8–10. In P-GR pigs, total leucocyte, neutrophil, monocyte, and eosinophil counts along with helper T cell fractions were elevated at 8–19 d of age, while the fraction of neutrophils with phagocytic capacity was reduced. Diarrhea and all remaining organ weights, blood chemistry, and immune variables were not affected by F-GR or P-GR.

Conclusion: Moderate GR before and after preterm birth has limited effect on systemic immune development in preterm pigs, despite marginal effects on immune cell populations, adrenocortical function, and body composition. Similar responses may be observed for preterm infants with moderate fetal and postnatal growth restriction.

Small fetal thymus and adverse obstetrical outcome: a systematic review and a meta-analysis

INTRODUCTION

The aim of this study was to explore the association between small fetal thymus on ultrasound and adverse obstetrical outcome.

MATERIAL AND METHODS

Medline, Embase, Cochrane and Web of Science databases were searched. Primary outcome was the risk of preterm birth before 37 and 34 weeks of gestation in fetuses with, compared to those without, a small thymus on ultrasound.

SECONDARY OUTCOMES

occurrence of chorioamnionitis, intrauterine growth restriction, neonatal sepsis, gestational age at birth, birthweight, neonatal morbidity and preeclampsia.

RESULTS

Twelve studies including 1744 fetuses who had ultrasound assessment of thymus during pregnancy were included. Women with preterm premature rupture of the membranes or with preterm labor were at higher risk of preterm birth before 37 weeks (p = 0.01), or before 34 weeks (p < 0.001) for fetuses with a small fetal thymus compared to those without a small thymus, and the risk of chorioamnionitis was higher when the thymus was small (p < 0.001). Fetuses with small thymus were not at higher risk of intrauterine growth restriction (p = 0.3). A small thymus increased the risk of neonatal sepsis (p = 0.007) and morbidity (p = 0.003), but not the risk of preeclampsia (p = 0.9).

CONCLUSIONS

A small fetal thymus is associated with a higher risk of preterm birth, chorioamnionitis, neonatal sepsis and morbidity, but not with intrauterine growth restriction and preeclampsia.

Enhanced thymocyte apoptosis induced by maternal undernutrition in late gestation results in declined mature T cells in rat fetal thymus

This study was designed to observe the effects of maternal food restriction (MFR) on the development of fetal thymus in different gestation periods. Timed pregnant rats were randomized into 3 groups: CN (free access to standard chow throughout gestation), MFR_0-21 (50% MFR throughout gestation), MFR_0-14 (50% MFR from gestational day (GD) 0 to GD14, early-mid gestation). Results showed that MFR during early-mid period had few impact on the fetal thymus and T cell subpopulations. However, MFR throughout gestation resulted in thymic atrophy, deceased frequency of both CD4⁺ and CD8⁺ single positive (SP) T cells and enhanced thymocyte apoptosis in fetus. Our results suggest the fetal thymus is more vulnerable to the adverse intrauterine environments in the late gestation period, and the decreased number of SP T cells could result from the enhanced thymocyte apoptosis.

Characterization of thymus-associated lymphoid depletion in bovine calves acutely or persistently infected with bovine viral diarrhea virus 1, bovine viral diarrhea virus 2 or HoBi-like pestivirus

Naïve pregnant cattle exposed to pestiviruses between 40-125 days of gestation can give birth to persistently infected (PI) calves. Clinical presentation and survivability, in PI cattle, is highly variable even with the same pestivirus strain whereas the clinical presentation in acute infections is more uniform with severity of symptoms being primarily a function of virulence of the infecting virus. The aim of this study was to compare thymic depletion, as measured by comparing the area of the thymic cortex to the medulla (corticomedullary ratio), in acute and persistent infections of the same pestivirus isolate. The same general trends were observed with each pestivirus isolate. Thymic depletion was observed in both acutely and persistently infected calves. The average thymic depletion observed in acutely infected calves was greater than that in age matched PI calves. PI calves, regardless of infecting virus, revealed a greater variability in amount of depletion compared to acutely infected calves. A trend was observed between survivability and depletion of the thymus, with PI calves surviving less than 5 weeks having lower corticomedullary ratios and greater depletion. This is the first study to compare PI and acutely infected calves with the same isolates as well as to evaluate PI calves based on survivability. Further, this study identified a quantifiable phenotype associated with potential survivability.

Acute Thymic Involution and Mechanisms for Recovery

Acute thymic involution (ATI) is usually regarded as a virulence trait. It is caused by several infectious agents (bacteria, viruses, parasites, fungi) and other factors, including stress, pregnancy, malnutrition and chemotherapy. However, the complex mechanisms that operate during ATI differ substantially from each other depending on the causative agent. For instance, a transient reduction in the size and weight of the thymus and depletion of populations of T cell subsets are hallmarks of ATI in many cases, whereas severe disruption of the anatomical structure of the organ is also associated with some factors, including fungal, parasitic and viral infections. However, growing evidence shows that ATI may be therapeutically halted or reversed. In this review, we highlight the current progress in this field with respect to numerous pathological factors and discuss the possible mechanisms. Moreover, these new observations also show that ATI can be mechanistically reversed.