Viral Infections

Cytomegalovirus. Cytomegalovirus (CMV) is the most common congenital viral disease in the United States. From 0.2% to 2.2% of all infants acquire infection during the perinatal period. The consequences of this infection can be devastating and include deafness, neurologic complications, developmental learning disabilities, multiple physical defects, and stillbirth. Infant mortality may be as high as 20% to 30% in primary CMV infections.

Unfortunately, the presence or absence of seroreactivity does not correlate with the presence or absence of the virus on body surfaces or in body secretions. Accurate diagnosis must be established by isolation of the virus from such sites as urine and endocervical secretions. Because there is no satisfactory therapy available for CMV infections in either adults or newborns, it is ideal for women who are pregnant or are contemplating pregnancy and are known to be seronegative to avoid exposure to CMV from such obvious sources as day-care centers and renal dialysis units.

Varicella-Zoster. Despite the fact that varicella infections are among the most common communicable diseases in the general population, they are relatively infrequent during pregnancy because most women have been infected with chickenpox as children.

Transmission of the virus to the fetus during the first 20 weeks of gestation has been reported to result in a clinical syndrome of intrauterine growth retardation, hypoplasia of the extremities, cutaneous scars, cortical atrophy, microcephaly, cataracts, chorioretinitis, microophthalmia, and psychomotor retardation. The exact risk of this congenital syndrome is unknown but is probably less than 1% to 2%.

A more common problem has been maternal varicella in the peripartum period, producing neonatal chickenpox. If a mother develops varicella within 4 days before delivery or 2 days after, there is a 25% chance that the newborn will become infected. During this interval the newborn acquires the virus but is delivered before the mother has produced a varicella-specific antibody response capable of crossing the placenta and protecting the fetus. Such infants may have as high as 30% mortality. When more than 5 days have elapsed between the onset of maternal rash and delivery, sufficient delay has occurred for a maternal antibody response to develop and the fetus is passively immunized, thus ameliorating the severity of the disease. If parturition occurs during the 7-day period of risk for disseminated neonatal infection, newborns should be passively immunized using varicella-zoster immune globulin.

Rubella. Rubella infection during the first trimester can lead to congenital rubella syndrome in greater than 80% of fetuses. Congenital rubella syndrome is characterized by intrauterine growth retardation, prematurity, increased risk for spontaneous abortion, and stillbirth, as well as severe neurologic, ophthalmologic, and cardiac complications. An estimated 10% to 15% of young adults remain susceptible to rubella, and limited outbreaks continue to be reported, particularly in universities and hospitals. Every effort should be made to vaccinate all nonpregnant young women unless there is proof of immunity or a specific contraindication to the vaccine. Because of the theoretic risk to the fetus, women should be counseled not to become pregnant for 3 months after vaccination.