Background: The risk of intrauterine cytomegalovirus (CMV) infection and disease in the fetus or newborn largely depends on time of primary maternal infection during pregnancy.
Objectives: Prospective cohort study of pregnancy outcome in relation to gestational age at primary maternal CMV infection.
Study design: In a total of 248 pregnancies with primary infection the onset of infection was determined by IgG seroconversion, IgG avidity and/or onset of clinical symptoms. Congenital infection was diagnosed by CMV detection in amniotic fluid, fetal tissue or urine of the neonate in the first 2 weeks of life. Clinical symptoms were retrieved from ultrasound and medical records.
Results: The intrauterine transmission rates following primary CMV infection in the pre- and periconceptional period were 16.7% (4/24) and 34.5% (10/29), respectively. For the first, second and third trimester of pregnancy transmission rates were 30.1% (25/83), 38.2% (29/76) and 72.2% (26/36), respectively. The rate of symptomatically infected fetuses or newborns at birth was 22.8% for any symptoms and 10.3% for severe manifestations. No symptoms were observed in infected newborns of mothers with primary infection in the preconceptional period and in the third trimester.
Conclusions: The risk of intrauterine transmission following primary maternal infection in the third trimester is high, but the risk of neonatal disease is low. The highest risk of severe symptoms in the fetus and newborn exists around conception and in the first trimester of pregnancy.
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