EP04.04: Trophoblast thickness in the first trimester of pregnancy using three‐dimensional ultrasound is associated with placental cytomegalovirus infection

Congenital cytomegalovirus (cCMV) infection is the most common congenital infection affecting 7 to 10 per 1,000 neonates and the first non-genetic cause of hearing loss in infants. Diagnosis of fetal infection is actually made by CMV-PCR in amniotic fluid from 17 week's. In this study, we investigated non-invasive markers to predict the fetal infection following maternal primary infection (MPI) before 14 weeks of gestation identified by serological screening. We conducted a single-centre retrospective study between October 2019 and April 2023. In our centre, CVS is offered to identify trophoblastic infection using CMV-PCR following MPI at between 2 months prior to conception and 12 weeks'. 3D-volumes of the trophoblast at 11-14 weeks' were systematically acquired before CVS. The maximum trophoblast thickness (MTT) measurement was conducted by two independent fetal medicine specialists blinded to both context and CVS results thanks to a standardised procedure. Maternal biomarkers included maternal serum markers used for Down syndrome screening collected at between 11+0 to 13+6 weeks' gestation, CMV-PCR in maternal blood and urines samples. 113 patients were enrolled in this study. Among them, 9 patients tested positive for CMV-PCR in trophoblast and 11 in amniotic fluid. The intraclass correlation coefficients was 0.832 (95% CI: 0.704 - 0.907) indicating a good agreement of MTT measurement among sonographers. MTT was significantly larger in case of positive CMV-PCR in trophoblast (p = 0.0012) and amniotic fluid (p = 0.0063). Prediction performance of fetal infection combining MTT and maternal markers was analysed using several models. MTT is associated with both placental and fetal infection following MPI. In this study, we identified a relevant, easy, and reproductible non-invasive marker for the diagnosis of fetal CMV infection. Further studies are needed to define the threehold of MTT. MTT may also be a candidate marker for non-primary maternal infection.