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

Abstract

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.

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

“…However, despite these results, it was reported in this review that ultrasound evaluation of the thymus is not yet sufficient in clinical practice to predict the perinatal outcome in pregnancies under these risks. Because there were many different threshold values, thymus measurement methods, and different demographic and laboratory markers reported in the studies 31 …”

“…Because there were many different threshold values, thymus measurement methods, and different demographic and laboratory markers reported in the studies. 31 A reduction in thymus gland size occurs as a result of cortical and medullary lymphocyte depletion. Many stress factors and environmental factors exposed during the perinatal period have been associated with the condition.…”

Antenatal diagnosis of chorioamnionitis: A review of the potential role of fetal and placental imaging

“…Meta‐analysis evidence of five studies into thymic involution demonstrated on ultrasound in the antenatal period shows a significant reduction in size of the thymus in fetuses affected by chorioamnionitis. Interestingly this is not upheld in other proinflammatory states such as pre‐eclampsia or intrauterine growth restriction, suggesting that this change is directly related to infection‐related innate immune activation, rather than inflammation itself 43 . Although this meta‐analysis includes 374 cases, there is high heterogeneity in the sample.…”

Middle-East OBGYN Graduate Education (MOGGE) Foundation Practice Guidelines: Prelabor rupture of membranes; Practice guideline No. 01-O-19

“…Pooled results from 5 of these studies showed increased rate of IAI among women at high risk (PROM and preterm labor) if fetal thymus measures small (OR = 16.0, 95% CI = 4.18-61.4). Furthermore, among women with PROM, the risk of neonatal sepsis increased (OR = 15.1, 95% 2.10-108) in the presence of small thymus, with a sensitivity and specificity of 95.0% (95% CI = 75.1-100) and 49.1% (95% CI = 41.2-57.0), respectively [71]. Analysis of these outcomes was limited by number of pooled patients (230 from 5 studies and 102 from 2 studies, respectively), significant heterogeneity, and wide range CI.…”