Systematic Serological Cytomegalovirus Screening in Pregnancy: Seroprevalence, Seroconversion and Frequency of Congenital Cytomegalovirus Infection from 2007 to 2016

Background: Cytomegalovirus infections (CMV) may have severe outcomes during pregnancy, but to date there are no evidence of efficacy for a systematic screening during pregnancy. A systematic serological screening of CVM infections in pregnancy has been active for some time in the Province of Trento, Northern Italy (540,000 inhabitants). Aims: To describe coverage and outcomes of the screening for CMV in pregnancy. Methods: The coverage and outcomes of the CMV screening were analyzed among women who delivered in the hospitals of the Province of Trento between 2007 and 2016 (n=47,407). As a primary information source, the birth assistance certificate (BAC) was used, a document required by Italian law which contains data regarding mother, pregnancy, birth and newborn. The missing data were retrieved through the hospital information system that records the clinical data of all patients.The cases of congenital CMV infection were defined on the basis of the positive new-born urine CMV DNA tests. Results: Serological CMV screening coverage rose from 59% in 2007 to 97% in 2016. No differences in coverage were observed in relation to age range, educational level and nationality at the end of the study period. The mean CMV infection seroprevalence rate during pregnancy is 70.3% (95% CI 69.8, 70.7) and it shifted from 56% in 2007 to 70% in 2016, for all pregnant women. The increase appears to be greater amongst foreign women. No differences were observed in seroprevalence according to age group and educational level. Over the period considered, 292 women seroconverted, equal to 0.77% (95% CI 0.76-0.78) of the total number of pregnant women tested for CMV. No differences were observed in the seroconversion rate in relation to the nationality, age group and educational level of the pregnant women. Primary infection accounts for 56% of cases of seroconversion and is more prevalent among Italian women and younger pregnant women. The urine test analysis showed that between 2007 and 2016, there were 76 cases of congenital neonatal infection, equal to 0.16% of all live births (0.18% in Italian women, 0.12% in foreign women). Sixty-six cases were associated with a primary infection of the mother, for a new-born infection transmission rate of 40% and 10 cases were associated with a nonprimary infection of the mother, for a new-born infection transmission rate of 5%. Conclusions: The availability of monitoring data regarding CMV infection during pregnancy, using the BAC database as information flow, makes it possible to perform area-based assessments. This opportunity is guaranteed on a local level by the implementation since the early 2000s of a birth attendance certificate template including a far greater number of variables than on the compulsory Italian Ministry of Health template. During the study period the coverage of CMV screening during pregnancy grew to include virtually all pregnant women receiving care in the province of Trento. This could be associated with a widespread awareness of the utility of the test during pregnancy, despite the lack of evidence regarding efficacy. The increase in seroprevalence can most likely be attributed to the gradual increase in the province of foreign women of childbearing potential and with the extension of the CMV test coverage during pregnancy. These two aspects could explain the increase over time in the seroconversion rate. The proportion of non-primary infection is higher than reported in literature: this result could be linked to a high seroprevalence. The rate of congenital infection is very low and equal to 0.16% of all live births. Due to the extension of screening during pregnancy, it was not found any difference in obstetric outcomes in relation to age classes, citizenship and educational level.