Pregnant women, their infants, at risk for genital herpes. (Stanford University)

One out of every 20 pregnant women enrolled in a study in Stanford, California, had an unsuspected risk of contracting herpes simplex virus type 2, the most common cause of genital herpes, from husbands who harbored the virus but had never had symptoms of the infection.

The Stanford University Medical Center team, led by Dr. Charles G. Prober, professor of pediatrics, also found that two-thirds of women infected with HSV-2 had no history of genital herpes symptoms and didn't know they were infected.

Taken together, the two findings "call out for a better test for HSV-2 and in turn, for wider screening of pregnant women and their sexual partners," said Dr. Prober. The research …