Transmission rates for primary infection are 30 to 36 percent in the first trimester, 34 to 40 percent in the second, and 40 to 72 percent in the third trimester (American College of Obstetricians and Gynecologists, 2017; Picone, 2017). In contrast, recurrent maternal infection infects the fetus in only 0.15 to 1 percent of cases. Naturally acquired immunity during pregnancy results in a 70-percent risk reduction of congenital CMV infection in future pregnancies (Fowler, 2003; LeruezVille, 2017). However, as noted earlier, maternal immunity does not prevent recurrences, and maternal antibodies do not prevent fetal infection (Ross, 2011) .
Newborns with apparent sequelae of in-utero-acquired CMV infection are described as having symptomatic CMV inection. Congenital infection is a syndrome that may include growth restriction, microcephaly, intracranial calcifications, chorioretinitis, mental and motor retardation, sensorineural deficits, hepatosplenomegaly, jaundice, hemolytic anemia, and thrombocytopenic purpura (Cheeran, 2009). An example of periventricular calcifications is shown in Figure 64-1. Of the estimated 40,000 infected neonates born each year, only 5 to 10 percent demonstrate this syndrome (Fowler, 1992). hus, most
FIGURE 64-1 Coronal view of cranial sonogram from a neonate with congenital cytomegalovirus infection showing multiple periventricular calcifications.
infected infants are asymptomatic at birth, but some develop late-onset sequelae. Complications may include hearing loss, neurological deicits, chorioretinitis, psychomotor retardation, and learning disabilities. Infections in dichorionic twins most 1ikely are nonconcordant (Egana-U grinovic, 2016).
Routine prenatal CMV serological screening is currently not recommended by the Society for Maternal-Fetal Medicine (2016). An algorithm for management is shown in Figure 64-2. Pregnant women should be tested for CMV if they present with a mononucleosis-like illness or if congenital infection is suspected based on abnormal sonographic indings. Primary infection is diagnosed using CMV-speciic IgG testing of paired acute and convalescent sera. CMV IgM does not accurately relect timing of seroconversion because IgM antibody levels may be elevated for more than a year (Stagno, 1985). Moreover, CMV IgM may be found with reactivation disease or reinfection with a new strain. Thus, specific CMV IgG avidity testing is valuable
Abnormal Maternal CMV Screening CMV IgG: positive CMV IgM: positive
CMV-specific IgG and IgM by EIA,
IgG avidity by EIA, and CMV-specific IgM by immunoblot
CMV IgG: negative CMV IgM: negative
CMV IgG: positive
IgG avidity index: high
CMV IgM: negative in conirming primary CMV infection. High anti-CMV IgG avidity indicates primary maternal infection >6 months before testing (Kanengisser-Pines, 2009). Finally, viral culture may be useful, although a minimum of 21 days is required before findings are considered negative.