Lymphocyte responses and virus excretion as risk factors for intrauterine infection with cytomegalovirus.

Serological screening of pregnant women in this and a previous study identified 28 cases of primary infection with cytomegalovirus, 7 (25%) of whom transmitted the infection to their fetuses. Risk factors for intrauterine infection were: 1) age less than 20 years, 2) Caucasian rather than non-Caucasian race, 3) a weak response to cytomegalovirus antigen in the lymphocyte transformation test, and 4) the excretion of cytomegalovirus in the urine. The greatest risk was when a weak lymphoproliferative response was detected in combination with a positive result for virus isolation, in which case the chance of fetal infection was 83%. Despite these associations, there was one important anomalous result of a woman who demonstrated a strong lymphocyte response during pregnancy and a negative result for virus isolation, but who gave birth to an infected baby who developed unilateral hearing loss.