None of my children had measles, mumps or rubella -

[Xipe Totec]

17. It is rare

Since so many adults are immune, not many pregnant women get chicken pox – estimates range from 1 to 7 cases for every 10,000 pregnancies. But if you're not immune and you do happen to catch the disease while you're pregnant, you could get quite sick, and there's a small chance that it would affect your baby. If you're not sure whether you're immune, a simple blood test can give you the answer.

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If you get chicken pox during the first or second trimester of pregnancy, there's a slight risk (probably less than 2 percent overall) that your baby will get something called congenital varicella syndrome (CVS). The risk is highest if you're infected between 13 and 20 weeks' gestation.

CVS is characterized by birth defects, most commonly skin scarring, malformed limbs, an abnormally small head, neurologic problems (like mental retardation), and vision problems. Plus, a baby with CVS may also grow poorly in utero and suffer from seizures and physical and mental developmental disabilities. The infection may also increase the risk of miscarriage or later fetal death.

http://www.babycenter.com/0_chicken-pox-during-pregnancy_9329.bc#articlesection1