Abstract

INTRODUCTION: 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 in fetuses with compared to those without a small thymus on ultrasound. SECONDARY OUTCOMES: occurrence of chorioamnionitis, intra-uterine growth restriction, neonatal sepsis, gestational age at birth, birthweight, neonatal morbidity and pre-eclampsia. RESULTS: Twelve studies including 1744 fetuses who had ultrasound assessment of thymus during pregnancy were included. Women with preterm premature rupture of the membranes (PPROM) or with preterm labour with a small fetal thymus were at higher risk of preterm birth <37 (p= 0.01), <34 (12.5 (p<0.001) weeks in fetuses with compared to those without 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 intra-uterine 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 pre-eclampsia (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 intra-uterine growth restriction and pre-eclampsia. This article is protected by copyright. All rights reserved.