CASE Anomalous findings on fetal anatomic survey
A 27-year-old previously healthy primigravid woman is at 18 weeks’ gestation. She is a first-grade schoolteacher. On her fetal anatomic survey, the estimated fetal weight was in the eighth percentile. Echogenic bowel and a small amount of ascitic fluid were noted in the fetal abdomen. The lateral and third ventricles were mildly dilated, the head circumference was 2 standard deviations below normal, and the placenta was slightly thickened and edematous.
What is the most likely diagnosis?
What diagnostic tests are indicated?
What management options are available for this patient?
Cytomegalovirus (CMV) is the most common of the perinatally transmitted infections, affecting 1% to 4% of all pregnancies. Although the virus typically causes either asymptomatic infection or only mild illness in immunocompetent individuals, it can cause life-threatening disease in immunocompromised persons and in the developing fetus. In this article, we review the virology and epidemiology of CMV infection and then focus on the key methods to diagnose infection in the mother and fetus. We conclude by considering measures that may be of at least modest value in treating CMV in pregnancy.
Virology of CMV infection
Cytomegalovirus is a double-stranded DNA virus in the Herpesviridae family. This ubiquitous virus is present in virtually all secretions and excretions of an infected host, including blood, urine, saliva, breast milk, genital secretions, and tissues and organs used for donation. Infection is transmitted through direct contact with any of the substances listed; contact with infected urine or saliva is the most common mode of transmission. Disease occurrence does not show seasonal variation.
After exposure, an incubation period of 28 to 60 days ensues, followed by development of viremia and clinical symptoms. In the majority of exposed individuals, CMV establishes a lifelong latent infection, and recurrent episodes of illness can occur as a result of reactivation of latent virus (also known as secondary infection) or, more rarely, infection with a new viral strain. In fact, most CMV illness episodes in pregnancy represent a reactivation of a previous infection rather than a new infection.
Following initial infection, both IgM (immunoglobulin M) and IgG (immunoglobulin G) antibodies develop rapidly and can be detected in blood within 1 to 2 weeks. IgM levels typically wane within 30 to 60 days, although persistence for several months is not unusual, and levels also can increase with viral reactivation (secondary infection). IgG antibodies typically persist for many years after a primary infection.
Intrauterine CMV infection occurs through hematogenous transplacental passage during maternal viremia. The risk of transmission and severity of fetal effects depend on whether or not the infection is primary or secondary in nature as well as the gestational age at fetal exposure.1,2
Additionally, postnatal vertical transmission can occur through exposure to viral particles in genital secretions as well as breast milk. CMV acquired in the postnatal period rarely produces severe sequelae in a healthy term neonate, but it has been associated with an increased rate of complications in very low birth weight and premature newborns.3
Continue to: Who is at risk...