As mentioned in the preceding section, it is possible to make a diagnosis of VZV infection by laboratory means if the illness seems atypical. Usually, however, the clinical presentation is characteristic enough to make laboratory confirmation of chickenpox or zoster unnecessary. PCR is the best means for documenting the congenital varicella syndrome (7). This might be performed on a skin biopsy of an affected area or cerebrebrospinal fluid. It is also possible to detect VZV antigens when children thought to have this syndrome develop zoster (7). Some of these infants may develop very mild manifestations of zoster, consisting of only a few vesicular lesions. Laboratory confirmation of VZV infection may be very useful in such situations.
Unfortunately, there are no reliable means to screen a woman to determine if her fetus has the congenital varicella syndrome (7). Although some fetuses have been shown to have abnormalities on ultrasound, diagnosis has never been subjected to careful study because the number of cases is extremely small. Moreover, some fetuses have been found to demonstrate calcification in the liver but have been normal at birth. It does seem from the literature, however, that a fetus identified to have a hypoplastic limb by ultrasound is highly likely to have the syndrome, and with the limb abnormality, there is a 40% chance that the infant will have either brain damage or early death. In such instances, if it is not too late in gestation, termination of the pregnancy should be strongly considered (7).
Most experts do not recommend termination when a woman has varicella during pregnancy unless obvious birth defects are present on ultrasound, as noted in this section (7). The risk to the fetus of being born with a serious birth defect due to varicella is on the order of about 2%, which is not much greater than the overall risk of 4% without varicella. Obviously, however, the caregiver needs to provide a great deal of counseling in this situation because of its uncertainties.
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