Neonatal varicella.

Neonatal varicella is mostly caused by maternal chickenpox acquired during the last 3 weeks of pregnancy. Transplacentally transmitted infections occur in the first 10 to 12 days of life, whereas chickenpox after that time is most likely acquired by postnatal infection. If the mother develops rash between days 4 and 5 antepartum to day 2 postpartum, generalized neonatal varicella leading to death occurs in up to 20% of affected cases. Neonatal chickenpox within the first 4 days after birth has usually been found to be mild. A fatal outcome has been reported in 23% of cases if neonatal chickenpox occurs between 5 and 10 to 12 days of age. Serological methods have been widely used to confirm clinical diagnosis. For rapid virological diagnostics, amplification of viral DNA in skin swabs by polymerase chain reaction is the method of choice. To prevent severe neonatal chickenpox, passive immunization is indicated. If varicella occurs, acyclovir treatment has to be administered promptly.