Varicella (Chicken Pox)

Varicella, also called chicken pox, is a viral disease that rarely occurs in adults as a primary infection. Up to 95% of women in childbearing age have antibodies against varicella virus. Infection of the fetus occurs in 1 to 5 per 10,000 pregnancies and induces a risk of birth defects called varicella embryopathy, to be evaluated prenatally by ultrasound. The manifestations may include microcephaly, chorioretinitis, cataract, microphthalmia, growth retardation, and developmental delay, more scarcely a hypoplastic limb. The risk varies depending on the timing of infection during pregnancy. Congenital varicella only occurs in case of primary infection during the first half of pregnancy. Varicella is more severe during pregnancy and might even be lethal for the mother. If a patient develops varicella 5 days or less before delivery or 1-2 days after delivery, there is a risk of neonatal varicella that can be very severe, and causes infant death in 30% of cases. If the patient develops varicella between 6 and 21 days before delivery, the newborn may develop a varicella, although the infection should be milder as the maternal antibodies partly protect the fetus.