Maternal human papillomavirus (HPV) infection is implicated as a cause of laryngeal papillomas in children. Children born to mothers infected with HPV appear to have the same type of HPV in their buccal mucosa as their mothers have in their cervix. Puranen and colleagues conducted a long-term prospective cohort study to determine the frequency of vertical exposure of an infant to the cervical HPV infection of the mother.

Cervical scrapings from 105 mothers and nasopharyngeal aspirate fluids from their 106 infants (including one pair of twins) were collected at the time of delivery. Either cytologic or histologic evidence of HPV infection was used to identify cervical HPV infection in 18 mothers. The DNA of HPV was identified by polymerase chain reaction and subsequent Southern blot hybridization.

Among 15 mothers who were DNA positive and had clinical signs of cervical HPV infection and were undergoing vaginal delivery, the samples of 13 (87 percent) of the mother-infant pairs showed the same type of HPV. A total of 60 mothers had no history or current clinical signs of cervical HPV infection. The same DNA type of HPV was found in both the mothers and their infants in 11 pairs, with different types of HPV found in two pairs. Results of DNA detection in infants born by cesarean section to the 26 mothers with no signs or history of HPV infection showed that five pairs had the same type of HPV infecton and two pairs had a different type. In 15 pairs, both mother and infant were DNA negative for HPV.

The overall concordance between HPV types in the mother and her infant was 69 percent. Regardless of match in type of HPV, 37 percent of infants were DNA positive for HPV infection. When the mode of delivery was separated, DNA of HPV was found in nine (35 percent) of the 26 infants born by cesarean section and in 30 (38 percent) of the 78 infants born by vaginal delivery. In the group of mothers with no history or signs of cervical HPV infection, DNA detection of HPV did not differ significantly between mothers and infants regardless of mode of delivery. The most frequent type of HPV found in both infant and mother was HPV-16 (10 pairs) followed by HPV-33 (three pairs).

Results demonstrated the possibility of exposure of the infant to HPV infection in utero. Data showed that five infants born by cesarean section were DNA-positive for HPV and harbored the same viral type as the mother. Because of the transient nature of HPV, it was not unexpected for the authors to find six infants whose nasopharyngeal aspirates proved DNA-positive for HPV even when the mother's cervical sample was DNA negative at the time of delivery.

The authors conclude that an infant is exposed to the cervical HPV infection of the mother even when there are no signs or history of infection and that transplacental exposure of an infant to HPV infection may be possible as well.

editor's note: Long-term studies relating pre-natal or intrapartum exposure to maternal HPV infection and subsequent development of respiratory papillomatosis in the infant are being conducted. Because there is high morbidity associated with respiratory papillomatosis, pregnant patients with clinical signs of HPV infection may request a cesarean section. On the basis of this study and others, a cesarean section does not appear to prevent the transmission of HPV infection to the infant. Long-term studies of infants positive for HPV are needed to further elucidate the mechanism of transmission and possible adverse sequelae.—b.a.