We sought to determine the sensitivity of maternal history as a predictor of varicella immune status during pregnancy. A total of 514 women were prospectively questioned about history of varicella infection at the time of their first prenatal visit. Eighty-one patients who gave either negative or uncertain histories of prior infection had blood drawn and analyzed for presence of varicella antibodies. Women with negative histories had a significantly lower rate of serologic varicella immunity than women with uncertain histories (46.9% vs 93.8%, p < 0.001); these women were also significantly younger than those with either uncertain or positive histories. Patient payer status and number of children were also analyzed; neither was significantly associated with varicella seropositivity. The certainty of a pregnant woman's varicella infection history was the strongest single predictor of her actual immune status. These results should be helpful both for patient counseling and for possible development of prenatal varicella screening protocols.