This pneumonia is particularly serious in a pregnant woman. This syndrome affects only about 2 percent of babies whose mothers were infected with chickenpox during the first 20 weeks of pregnancy, and is rare if infection occurs after 20 weeks. Another risk is severe chickenpox infection in the newborn, which occurs when a mother develops the rash from 5 days before to 2 days after delivery. Between 25 and 50 percent of newborns become infected, and develop a rash between 5 and 10 days after birth. Without treatment, up to 30 percent of infected babies die.
Most treated babies have a mild illness.
If serious symptoms develop in spite of treatment with VZIG, antiviral drugs can help. If a mother develops the rash between 6 and 21 days before delivery, the baby faces some risk of mild infection. About seven women in 10,000 will develop chickenpox during pregnancy. During a preconception or early prenatal visit, a woman's health care provider will ask whether she has already had chickenpox. If she has not, or does not know, her provider may recommend a blood test that will show whether she is immune.