Primary human cytomegalovirus (HCMV) infection occurring in pregnant women within 3 months before (preconceptional) or within 4 weeks after (periconceptional) the last menstrual period represents an as-yet-undefined risk to the fetus. One (9.1%) of 11 newborns born to 12 women with preconceptional infection was subclinically infected (1 aborted fetus was not examined for infection). Of 20 pregnancies in women with periconceptional infection, 7 were terminated before 12 weeks of gestation (aborted fetus was not examined), 1 was terminated at 23 weeks after prenatal diagnosis of congenital infection, and 12 continued to term. Of those 12, 3 resulted in newborns who were congenitally infected. Thus, in the periconceptional group, intrauterine transmission occurred in 4 (30.8%) of 13 pregnancies for which the virologic outcome was known. One newborn was symptomatic at birth, and disseminated HCMV infection was diagnosed in an aborted fetus. Periconceptional primary HCMV infection seems to bear a higher risk of unfavorable outcome than preconceptional infection, and counseling should be adjusted accordingly.