If a pregnant woman comes in contact with a case of chickenpox, it is necessary to ascertain whether the exposure was significant and if the pregnant woman is non-immune. Household contact, face-to-face contact with a case of chickenpox for at least 5 minutes or a contact indoor with a case of chickenpox for more than one hour have been considered to constitute a significant exposure. A British Working Group felt that any close contact should be considered significant (14), although it conceded that transient exposure e.g. a waiting room or in public transport, is unlikely to pose a significant threat of infection. Women with definitive history of chickenpox in past could be considered immune but those without such history or with indeterminate history should have their immune status against chickenpox determined. Some authorities feel that all pregnant women who have a significant exposure to chickenpox, should get their immune status determined; irrespective of past history of chickenpox (28). Pregnant women found to be non-immune should receive varicella zoster immune globulin as soon after the exposure as possible (29,30). It is most efficacious if administered within 72 hours of exposure, but there is evidence to indicate benefit for up to 10 days following exposure (14). Studies suggest that VZIG may modify or prevent disease in the mother.

Pregnant mothers should be told about the possible manifestations of chickenpox and be requested to report to their physician at the first sign of chickenpox. They should avoid contact with other susceptible individuals, including other pregnant women and neonates.

If a pregnant woman is infected in the first 20 weeks of pregnancy, the risk of developing embryopathy could be close to 1% (12). One study has reported that giving VZIG to women who have already developed chickenpox may help prevent fetal infection (31). Prospective studies will have to be carried out before a general recommendation is made regarding using VZIG in such circumstances. The second issue concerns the use of acyclovir in a pregnant woman. Acyclovir is a highly effective anti-viral drug against varicella. However, its safety in pregnancy has not been extensively studied and is not cleared for use during pregnancy. However, when a pregnant woman develops first sign of varicella pneumonitis, it seems reasonable to use intravenous acyclovir to treat such a woman who is facing a potentially fatal condition. Acyclovir is known to decrease the time to cutaneous healing, lessen symptoms and fever when administered to immunocompetent non-pregnant individuals within 24 hours of the onset of the rash. Extrapolating these observations to pregnant women, some experts advice that oral acyclovir be administered to women in the second half of pregnancy presenting within 24 hours of the onset of the rash (14). It is possible that if acyclovir is given prophylactically to women with chickenpox, it will reduce the risk of fetal varicella syndrome. However, studies to evaluate this aspect have not been undertaken. Nevertheless, some have suggested admission of all pregnant women with varicella to hospital for early acyclovir treatment (31). There is some debate about the safety of acyclovir in the fetus, but solace could be found in the fact that fetal anomalies have not been detected when acyclovir was used in early pregnancy (31,32,33). The various therapeutic modalities used for managing exposure to / or infection with VZV during pregnancy are summarized in Table 2.

As started earlier, neonates born to women who develop chickenpox within 5 days before delivery or within two days after delivery are at increased risk for systemic life-threatening disease. These neonates should receive VZIG as soon as possible, so as to attenuate neonatal infection or prevent it totally (34,35,36). It should, however, be remembered that VZIG may not be able to prevent each and every case even when it is administered on the first day of life. Immature cell mediated immunity is the likely window allowing the infection to break through. These babies should be kept under surveillance for 16 days to make sure that they have not developed infection. Normal immunoglobulin preparations for intravenous use (IVIG) also provide sufficient amount of antibodies against VZV. Hence, IVIG could be used for the purpose if VZIG is not available.

If an infant does develop chickenpox, he should receive intravenous (and not oral) acyclovir at a dosage of 500 mg/m2 every 8 hours (or 10-15 mg/kg/dose - 8 hourly) for 5 to 7 days or until there is good evidence of crusting and no further lesion formation (2,27,37,38). Intravenous or oral acyclovir therapy should also be considered in other infants with congenital varicella and severe clinical disease (14).

Horizontal transmission of varicella in maternity wards or nurseries is unusual. Most neonates are protected by maternally derived antibody and exposure is usually brief and non-intimate. However, premature babies (<30 week gestational age, < 1 kg. weight) or infants born to mothers with negative history of chickenpox could be susceptible to varicella infection. VZIG may be administered to all such infants. Alternatively, they may be screened rapidly for VZV antibody and VZIG administered to only susceptible neonates who have had a significant exposure. Some experts administer VZIG to all neonates following exposure (14,39,40,41).