Congenital cytomegalovirus (CMV) infection is the most common congenital infection with a birth prevalence of 0.4% in Europe. It is the leading non-genetic cause of sensorineural hearing loss and a major cause of neurodevelopmental disabilities. The risk of intrauterine transmission is highest when primary infection occurs during pregnancy. Primary CMV infection is asymptomatic or causes non-specific symptoms and only serology can diagnose it with certainty. The diagnosis of CMV infection is based on the combination of 2 or 3 serological markers and the interpretation of the results is more complex than for other infections and may require additional analyses and sometimes delay the diagnosis and the implementation of secondary prevention of CMV transmission to the fetus by the administration of valaciclovir. Indeed, the effectiveness of secondary prevention is conditioned by the early administration of treatment after the maternal primary infection. The National Reference Center for Congenital CMV Infections at Necker Hospital, in collaboration with the virology laboratory at Paul Brousse Hospital, has developed the MyCMV expert tool, which is a decision-making algorithm that allows the interpretation of CMV serology and CMV PCR results. The hypothesis of the study is that the use and provision of this MyCMV expert tool to health professionals (biologists, midwives and obstetricians) for the interpretation of virological results could avoid a delay in diagnosis and would allow patients to be referred more quickly to a prenatal diagnosis center for appropriate management of CMV infection. The aim of the study is to evaluate the rate of detection of primary CMV infection in the first trimester of pregnancy using the MyCMV tool compared with the reference method (results interpreted by the centre's expert investigator).