Chickenpox rarely occurs as a primary infection during pregnancy. There is a risk of foetal malformation only if the mother is infected before 20 weeks of gestation. The two main problems encountered for antenatal diagnosis of congenital varicella are the rare incidence of morphology anomalies (less than 35%) and the difficulty of establishing a functional prognosis. Echography is used to detect foetal malformations. In suspected cases the proof of viral infection can be based on results of foetal serology, viral culture or polymerase chain reactions. According to the literature, echographically detected malformations in cases with certain foetal infection have a poor outcome although conflicting cases have been reported.