To determine the prevalence and association of human papillomavirus (HPV) infection in the cervices and placentas of pregnant women. Cervical samples were taken from 179 of 226 women who had placental biopsies because of abnormal ultrasound findings or were older than 35 years, to detect HPV infections with hybrid capture II tests. Polymerase chain reaction (PCR) was done on placental tissue of 147 of the 226 women to detect HPV DNA. We found 44 of 179 women (24.6%, 95% confidence interval 18.3, 31.0) to test positive for HPV in their cervices. Logistic regression analyses showed decreased prevalence of HPV infection with increased maternal age (P =.039). The HPV DNA E6 PCR from the villus tissue was negative in the 147 cases examined. However, a significant contingency coefficient between low-risk HPV infection and elevated risk of chromosome aberration was found (φ = V = 0.15, P =.050). The infection rate of 24.6% in women without clinical symptoms of HPV infection was high, but there seemed to be no virus transmission to the placenta in women with subclinical infections. Low-risk cervical HPV infection might be associated with a slightly higher risk of abnormal fetal karyotype.