Comparative sonographic measurement of the fetal thymus size in singleton and twin pregnancies

OBJECTIVES

The aim of this study was to compare the size of the thymus gland of healthy fetuses in twin and singleton pregnancies using the thymic-thoracic ratio (TTR). As a second objective, the TTR difference between monochorionic and dichorionic twin thymus size was examined. Finally, a possible correlation between thymus size and gestational age (GA) at birth in twin pregnancies was investigated.

METHODS

The TTR was measured retrospectively using the plane of three-vessel view in prenatal ultrasound examinations. Images of 140 healthy twin fetuses (33 monochorionic and 107 dichorionic) between 19+0 and 33+2 weeks of gestation were utilized and compared to 248 healthy singleton fetuses.

RESULTS

A significant difference in thymus size could be observed between healthy fetuses from singleton and twin pregnancies (p<0.001). Thymus size in monochorionic and dichorionic fetuses did not differ. If only comparing fetuses after 37+0 weeks of pregnancy, the difference in the TTR was no longer significant. In addition, an association between prematurity and larger thymus was established. However, the effect size of this association was small.

CONCLUSIONS

The results indicate that factors related to preterm birth, rather than the number of fetuses, are likely to influence the TTR. Utilizing fetal thymus size in ultrasound screening may hold potential for predicting adverse events like preterm birth in both singleton and twin pregnancies, but only in addition to other variables.

Assessment of fetal thymus size in pregnancies of underweight women

OBJECTIVES

The aim of this study was to compare the fetal thymus size measured in the second and third trimester of pregnancy in underweight women and women with normal weight. We hypothesized that the low maternal weight would affect the fetal thymus size, as maternal health and nutrition during pregnancy affect fetal development, including that of the fetal immune system.

METHODS

The fetal thymus size was retrospectively assessed by determining the thymic-thoracic ratio in 77 pregnancies of underweight women (study group) and 85 pregnancies of women with normal weight (control group) between the 19th and 34th week of pregnancy. The anteroposterior thymic diameter and the intrathoracic mediastinal diameter were measured in the three-vessel view acquired from routine echocardiograms. The thymic-thoracic ratio was calculated by dividing the anteroposterior thymic diameter with the intrathoracic mediastinal diameter. Additionally, we compared the descriptive data between the two groups, such as gestational age at screening and at birth, birth weight, umbilical artery pH and APGAR-score after 5 min.

RESULTS

The mean fetal thymic-thoracic ratio in underweight women was not significantly different to that in normal weight pregnancies (0.374 vs. 0.363). However, the average gestational age at birth, birth weight and APGAR-score at birth were lower in the group of underweight women.

CONCLUSIONS

There is no evidence that low maternal weight influences fetal thymus size during pregnancy. The differences we observed concerning fetal weight at birth, gestational age at delivery, APGAR-Score and birth weight percentile confirm the results of previous studies.

Evaluation of fetal thymus size in maternal autoimmune diseases: systemic lupus erythematosus, Sjögren's syndrome and antiphospholipid antibody syndrome

PURPOSE

To investigate the effect of inflammation on the fetal thymus-thoracic ratio (TTR) in pregnant women with systemic lupus erythematosus (SLE), Sjögren's syndrome (SS) and antiphospholipid antibody syndrome (APS).

METHOD

This prospective case-control study included 45 pregnant women with SLE, SS, and APS and 90 gestational age-matched healthy pregnant women between 24 and 37 gestational weeks. The ratio of the anteroposterior fetal thymus length to the transverse mediastinal length was calculated as the TTR in the study groups.

RESULTS

Fetal TTR was significantly lower in the case group (p < 0.001). Fetal TTR in the APS group was significantly lower than SS group (p = 006). The patients using hydroxychloroquine (HCQ) had significantly higher fetal TTR compared to patients not using HCQ (p = 0.004). A moderate negative correlation was found between the disease duration and fetal TTR (r =  - 0.552, p < 0.001). In predicting admission to the neonatal intensive unit care (NICU), a value of 0.31 was found for the fetal TTR with a sensitivity of 83.3% and a specificity of 69% CONCLUSION: Maternal inflammation in pregnancies with autoimmune diseases may affect the intrauterine milieu of the fetus and cause a lower fetal TTR. Additionally, the lower level of fetal TTR may be more effective and beneficial for the clinician if combined with other risk factors in predicting NICU admission.

Small fetal thymus and adverse perinatal outcome in maternal vasculitis: A prospective case-control study

BACKGROUND

Ultrasonographic evaluation of fetal thymus size may be used to predict the adverse perinatal outcome in pregnant women with vasculitis.

AIM

To compare fetal thymus size in pregnant women with vasculitis and healthy pregnant women and to evaluate whether fetal thymus size predicts the adverse perinatal outcome.

METHODS

Twenty-two pregnant women with previously diagnosed vasculitis, 18 of them with Behçet's disease, three with Takayasu arteritis, and one with Wegener's granulomatosis, were included in the case group. The control group comprised 66 healthy pregnant women whose gestational ages matched the case group. Thymic thoracic ratio (TTR) was measured to assess fetal thymus size in the view of three vessels and trachea.

RESULTS

In the case group, fetal TTR was significantly lower (0.32 ± 0.03 vs. 0.36 ± 0.02, p = < 0.001). Fetal TTR was significantly lower in those using prednisone than those not (p = .001) in the case group. There was no significant difference in fetal TTR between colchicine used and not used (p = .078) in the case group. Also, for the TTR, a sensitivity of 100% and a specificity of 92% were achieved with a cut-off value of 0.33 for predicting adverse perinatal outcomes.

CONCLUSION

The fetuses of pregnant women with maternal vasculitis had a smaller TTR. The small fetal thymus may alert clinicians to possible adverse perinatal outcomes and, with other supporting risk factors, may help predict adverse perinatal outcomes in pregnant women with vasculitis.

An enlarged fetal thymus may be the initial response to intrauterine inflammation in pregnant women at risk for preterm birth

OBJECTIVE

Fetal thymus involvement in prematurity has been studied, and this study aimed to evaluate its relationship with short cervix and amniotic fluid sludge in the second trimester of pregnancy.

METHODS

In this prospective cross-sectional study, 79 pregnant women (19+0 to 24+6 weeks) were included, and cervical length and the presence or absence of amniotic fluid sludge were evaluated. In the three-vessel view of the fetal thorax, the thymus was identified, and its perimeter and transverse diameter were measured and transformed to a zeta score based on gestational age.

RESULTS

Data from 22 women with short cervix (<25 mm) and 57 patients with normal cervix (≥25 mm) were analyzed. The transverse diameter of the fetal thymus was significantly greater in the short cervix group compared to that of the normal cervix group (z-score 2.708 vs. -0.043, p=0.003). There were no significant differences in the perimeter (z-score -0.039 vs. -0.071, p=0.890) or the transverse diameter (z-score 1.297 vs. -0.004, p=0.091) of the fetal thymus associated with the presence (n=21) or absence of sludge (n=58).

CONCLUSION

A short cervix is associated with an increased transverse diameter of the fetal thymus during the second trimester of gestation.

Decreased fetal thymus size at 24 weeks gestation by ultrasound measurement in gestational diabetes mellitus fetal thymus examination for diabetes

AIM

This study aimed to evaluate the difference in fetal thymus diameter, which we measured ultrasonographically, between the healthy pregnant group and the pregnant group with gestational diabetes.

METHOD

Fetal thymus and thymus/thorax ratio parameters were assessed in this case-control study. Patients were examined in two groups. They included 49 diabetics (study group) women and 71 nondiabetic (control group). We performed a binary logistic regression analysis to determine the predictive value of ultrasonographic measurements. We completed the receiver curve characteristic analysis to evaluate the cut-off thymus diameter.

RESULTS

The median age of pregnant women was 27. Thymus diameter and thymus-thorax ratio were smaller in fetuses of diabetic mothers than in the nondiabetic group (p <0.05). Thymus diameter was found to be more predictive of gestational diabetes prediction (p: 0.019). There was no correlation between fasting blood glucose and thymus diameter.

CONCLUSION

Decreased fetal thymus anterior-posterior diameter seems to be associated with diabetic pregnancy.

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.

Maternal High-Fat Feeding Affects the Liver and Thymus Metabolic Axis in the Offspring and Some Effects Are Attenuated by Maternal Diet Normalization in a Minipig Model

Maternal high-fat diet (HFD) affects metabolic and immune development. We aimed to characterize the effects of maternal HFD, and the subsequent diet-normalization of the mothers during a second pregnancy, on the liver and thymus metabolism in their offspring, in minipigs. Offspring born to high-fat (HFD) and normal diet (ND) fed mothers were studied at week 1 and months 1, 6, 12 of life. Liver and thymus glucose uptake (GU) was measured with positron emission tomography during hyperinsulinemic-isoglycemia. Histological analyses were performed to quantify liver steatosis, inflammation, and hepatic hematopoietic niches (HHN), and thymocyte size and density in a subset. The protocol was repeated after maternal-diet-normalization in the HFD group. At one week, HFDoff were characterized by hyperglycemia, hyperinsulinemia, severe insulin resistance (IR), and high liver and thymus GU, associating with thymocyte size and density, with elevated weight-gain, liver IR, and steatosis in the first 6 months of life. Maternal diet normalization reversed thymus and liver hypermetabolism, and increased HHN at one week. It also normalized systemic insulin-sensitivity and liver fat content at all ages. Instead, weight-gain excess, hyperglycemia, and hepatic IR were still observed at 1 month, i.e., end-lactation. We conclude that intra-uterine HFD exposure leads to time-changing metabolic and immune-correlated abnormalities. Maternal diet-normalization reversed most of the effects in the offspring.

Correlation of first-trimester thymus size with chromosomal anomalies

OBJECTIVES

The aim of this study was to investigate the correlation between fetal thymus size measured during first-trimester screening and chromosomal anomalies.

METHODS

This study is a retrospective evaluation, in which the anterior-posterior diameter of the thymus in a midsagittal plane was measured in first-trimester ultrasound between 11⁺⁰ and 13⁺⁶ weeks of gestation in 168 fetuses with chromosomal anomalies (study group) and 593 healthy fetuses (control group). The included cases were subdivided into six groups: (1) trisomy 21, (2) trisomy 18, (3) trisomy 13, (4) Turner syndrome, (5) triploidy and (6) normal controls. Thymus size measurements were adjusted to the week of gestation, which was determined by ultrasound using crown-rump-length (CRL), by calculating a ratio between CRL and thymus size (CRL-thymus-ratio). Each study group was compared with the control group separately.

RESULTS

Thymus size in fetuses affected by trisomy 18 or trisomy 13 was noticeably smaller compared to the control group (1.4 mm [1.3, 1.5] and 1.3 mm [1.2, 1.4] vs. 1.8 mm [1.6, 2.1]; all p<0.001; respectively). The thymus size of fetuses with trisomy 21 and Turner syndrome did not differ from healthy fetuses. Between the CRL-thymus-ratios of the separate study groups no statistically noticeable differences could be found.

CONCLUSIONS

Fetal thymus size appeared to be smaller in pregnancies affected by trisomy 18 and trisomy 13. The predictive value of fetal thymus size in first-trimester screening should be evaluated prospectively.

Influence of maternal HIV infection on fetal thymus size

Objective To reveal the effect of a maternal human immunodeficiency virus (HIV) infection on the fetal thymus size. Methods The sonographic fetal thymus size was measured retrospectively in 105 pregnancies with maternal HIV infection and in 615 uncomplicated singleton pregnancies. The anteroposterior thymic and the intrathoracic mediastinal diameter were determined in the three-vessel view and their quotient, the thymic-thoracic ratio (TT ratio), was calculated. The study group was subdivided into three groups by the maternal viral load on the date of ultrasound (<50 cop./mL, 50-1000 cop./mL, >1000 cop./mL). Furthermore, an association between prognostic factors of the HIV infection such as the lymphocyte count, CD4/CD8 ratio, HIV medication and the thymus size, was investigated using correlation analyses. Results Fetal thymus size in pregnancies of HIV-positive mothers showed to be noticeably larger than in uncomplicated pregnancies. The mean TT ratio in the HIV-positive group was 0.389 and in the control group 0.345 (P < 0.001). There was no association between any maternal HIV parameter or medication and the size of the thymus gland. Conclusion Maternal HIV infection was associated with an increased fetal thymus size. Further consequences of intrauterine HIV exposure for fetal outcome and the development of the immune system of HIV-exposed uninfected (HEU) infants must be discussed.

Measuring fetal thymus size: a new method for diabetes screening in pregnancy

Objective: To investigate the correlation between fetal thymus size and diabetes in pregnancy.Method: Fetal thymus size was assessed in 160 pregnant women with gestational age of 19-39 weeks. They included 80 diabetic (investigation group) and 80 nondiabetic (control group) women. Fetal thymus size was measured by thymic-thoracic ratio. We did this with dividing the thymus' anteroposterior diameter by anteroposterior of mediastinum.Results: Thymic-thoracic ratio was significantly smaller in fetuses of diabetic mothers compared to the nondiabetic group (p = .001). It remained significant after subgrouping diabetic mothers into overt diabetes, insulin-dependent gestational diabetes, and noninsulin-dependent gestational diabetes.Conclusion: Although thymus size was smaller in fetuses of diabetic pregnant women compared to nondiabetic pregnant women, it seems that thymic-thoracic ratio can be a predictor of diabetes and its other related adverse effects during pregnancy.

Foetal thymus size in pregnancies after assisted reproductive technologies

PURPOSE

The aim of our study was to compare thymus sizes in foetuses conceived using assisted reproductive technologies (ART) to those conceived naturally (control group).

METHODS

Sonographic foetal thymus size was assessed retrospectively in 162 pregnancies conceived using ART and in 774 pregnancies conceived naturally. The anteroposterior thymic and the intrathoracic mediastinal diameter were measured to calculate the thymic-thoracic ratio (TT-ratio). The ART cases were subdivided into two groups: (1) intracytoplasmic sperm injection (ICSI; n = 109) and (2) in vitro fertilisation (IVF; n = 53).

RESULTS

The TT-ratio was smaller in pregnancies conceived using ART (p < 0.001). In both ART subgroups (ICSI and IVF), the TT-ratio was lower compared to the control group (p < 0.001). However, no difference between the two subgroups could be detected (p = 0.203).

CONCLUSIONS

Our data show reduced thymus size in foetuses conceived using ART compared to controls. These findings indicate that the use of ART may lead to certain deviations in organogenesis.