EP04.01: First trimester diagnosis of cytomegalovirus trophoblastic infection using CMV‐PCR: prediction of fetal CMV infection and symptoms at birth

CMV-PCR in chorionic villi sampled at 14 weeks' can diagnose trophoblastic infection. We aimed to assess its value to predict fetal CMV infection as well as symptoms at birth. Pregnant women referred for CMV maternal primary infection in early pregnancy between October 2019 and March 2023 as a result of serological screening were offered secondary prevention by valaciclovir and chorionic villus sampling for CMV-PCR at around 14 weeks' followed by amniocentesis from 17 weeks'. Follow-up of infected fetuses included ultrasound and MRI. All newborns were tested for infection and related symptoms at birth. 139 women were included including 134 women with both CVS and amniocentesis and 5 with negative CMV-PCR in CVS and at birth. 8/11 fetuses with CMV-PCR positive in trophoblast were also infected in amniotic fluid. CMV-PCR in amniotic fluid was positive in 7/128 patients with a negative CMV-PCR in trophoblast. Sensitivity, specificity, positive (PPV) and negative predictive (NPV) values of CMV-PCR in trophoblast to predict positive CMV-PCR in amniotic fluid was 53.3%, 97.5%, 72.7% and 94.5% respectively. No case of fetal infection occurred in “triple negative CMV-PCR” (trophoblast, maternal blood and urine in the first trimester). 12/124 patients with negative PCR in amniotic fluid had a positive PCR at birth, without any symptoms during pregnancy or at birth. 5 infected newborns were symptomatic at birth. Two newborns with bilateral sensorineural hearing loss had positive PCR in trophoblast and were not treated during pregnancy Secondary prevention by valaciclovir was associated with asymptomatic state at birth (p = 0.043). Specificity and NPV of CMV-PCR on trophoblast to predict symptomatic infection at birth was 94.0% and 98.4% respectively. CMV-PCR on trophoblast has a high-negative predictive value for fetal infection and a high specificity and negative predictive value for symptomatic infection at birth following MPI.