Rubella. Congenital Rubella Syndrome, страница 2

A variety of tests have been proposed for the diagnosis of congenital rubella syndrome. Cordocentesis can be performed to determine the total serum IgM concentration in fetal blood and to detect viral-specific antibody. However, fetal immunoglobulin production usually cannot be detected prior to 19 to 22 weeks of gestation. Some authors have proposed chorionic villus sampling (CVS) as a diagnostic test because placental tissue infected with rubella virus produces a cytopathic effect when grown in tissue culture. Viral antigen also can be identified rapidly in tissue culture by RNA-DNA hybridization techniques, and amniotic fluid can be cultured for rubella virus. Unfortunately, although the tests outlined above can demonstrate that rubella virus is present in the fetal compartment, they do not indicate the degree of fetal injury. Accordingly, detailed ultrasound examination is the best test to determine if serious fetal injury has occurred. Abnormalities that can be identified accurately by ultrasound include intrauterine growth restriction, microcephaly, and cardiac malformations.

The prognosis for infants with congenital rubella syndrome is guarded. [194] [195] [196] Approximately 50 percent of affected individuals have to attend schools for the hearing impaired. An additional 25 percent of infected children require at least some special schooling because of hearing impairment, and only 25 percent are able to attend mainstream regular schools. Some affected individuals develop insulin-dependent diabetes later in life, presumably secondary to in utero infection of the pancreas. The estimated lifetime cost of caring for a child with congenital rubella syndrome is approximately $200,000 to $300,000.

Obstetric Management

Ideally, women of reproductive age should have a preconception appointment when they are contemplating pregnancy. At this time, they should be evaluated for immunity to rubella. If serologic testing demonstrates that they are susceptible, they should be vaccinated with rubella vaccine prior to conception. [189] When preconception counseling is not possible, all obstetric patients should have a test for rubella at the time of their first prenatal appointment. Women who are susceptible to rubella should be counseled to avoid exposure to other individuals who may have viral exanthems.

If a susceptible patient is subsequently exposured to rubella, serologic tests should be obtained to determine whether acute infection has occurred. If acute infection is documented, patients should be counseled about the risk of congenital rubella syndrome. Obviously, specific counseling should be based on the time in gestation when maternal infection occurred. The diagnostic tests for detection of in utero infection should be reviewed. Patients should be offered the option of pregnancy termination based on the assessed risk of serious fetal injury. [192]

Susceptible patients who are fortunate enough to escape infection during pregnancy should be vaccinated immediately postpartum. The present rubella vaccine is the RA 27/3 preparation. It is much more immunogenic than the earlier HPV-77 and Cendehill vaccines and is available in a monovalent form, bivalent form (measles-rubella, MR), and trivalent form (measles-mumps-rubella, MMR). Approximately 95 percent of patients who receive rubella vaccine seroconvert. Antibody levels persist for at least 18 years in more than 90 percent of vaccinees.

There are few adverse effects of vaccination, even in adults. Less than 25 percent of patients experience mild constitutional symptoms such as low-grade fever and malaise. Less than 10 percent experience arthralgias, and less than 1 percent develop frank arthritis. Interestingly, when the vaccine is administered in the immediate postpartum period, these adverse effects are often delayed for up to 21 days. Women who have received the vaccine cannot transmit infection to susceptible contacts, such as younger children in the home. Breast-feeding is not a contraindication to vaccination. In addition, the vaccine can be administered in conjunction with other immunoglobulin preparations such as Rh-immune globulin.

Women who receive rubella vaccine should practice secure contraception for a minimum of 3 months after vaccination. For a number of years, the CDC maintained a registry of women who received the rubella vaccine within 3 months of conception. That registry included almost 400 patients, and, fortunately, there were no instances in which congenital rubella syndrome resulted from vaccination. [197] However, there were cases in which women elected to have abortions following vaccination and rubella virus was isolated from the products of the conception. The maximum theoretical risk of congenital rubella resulting from rubella vaccine in early pregnancy is 1 to 2 percent.