Human Papillomavirus (HPV) is an extremely common group of viruses; most sexually active individuals acquire an infection at some point. While many HPV infections are transient and cause no symptoms, the virus can cause genital warts and several types of cancer. Expectant parents who carry the virus often wonder about passing it to their child, a process known as vertical transmission. Although exposure during pregnancy or birth is possible, the development of a clinical condition in the infant remains a rare event.
Understanding Vertical Transmission
Vertical transmission refers to the passage of a pathogen from a mother to her child, occurring before birth, during delivery, or postpartum. The most recognized route for HPV transmission is during passage through the birth canal. This happens when the infant contacts infected cells or secretions in the mother’s lower genital tract during a vaginal delivery. Studies show that newborns delivered vaginally have a higher rate of HPV detection compared to those delivered by Cesarean section, suggesting direct exposure during birth is the primary mechanism.
The rate of HPV detection in newborns born to HPV-positive mothers varies widely, ranging from 3% to nearly 80%, with some meta-analyses suggesting an overall transmission probability around 25%. However, detecting viral DNA at birth often represents a temporary inoculation rather than a persistent infection. The risk of transmission is higher when the mother has a high viral load or visible lesions, such as genital warts, in the birth canal. For instance, one study found the transmission probability was about 11% for a vaginal delivery compared to less than 4% for a Cesarean section.
Transmission of HPV before birth, known as in utero transmission, is extremely rare but biologically plausible. HPV particles have been detected in the placenta, amniotic fluid, and umbilical cord blood, suggesting the virus could potentially cross the placental barrier. This route is not well understood; the vast majority of HPV cases in infants are attributed to exposure during delivery. The HPV types most frequently associated with transmission are the low-risk types 6 and 11, which cause genital warts.
Potential Health Effects in Children
For the majority of exposed infants, the HPV infection is transient and clears without causing symptoms or long-term health issues. Most infants who test positive for HPV DNA at birth will test negative within a few months to two years, indicating their immune system has successfully fought off the virus. This temporary presence of the virus does not typically result in clinical disease.
The most serious consequence of vertical HPV transmission is Juvenile-Onset Recurrent Respiratory Papillomatosis (RRP). RRP is a rare condition characterized by the growth of benign, wart-like tumors in the respiratory tract, most commonly in the larynx (voice box). This condition is almost exclusively caused by the low-risk HPV types 6 and 11, acquired during birth. The estimated incidence of RRP is very low, affecting approximately one to four children per 100,000 births.
The tumors in RRP can obstruct the airway, leading to symptoms like persistent hoarseness or a weak cry in infants. As the lesions grow larger, they can cause noisy breathing (stridor) and difficulty breathing, requiring immediate medical attention. Children diagnosed with RRP, particularly before age three, often require repeated surgical procedures to remove the growths and maintain an open airway. These interventions are not a cure, as the papillomas frequently grow back, sometimes requiring monthly procedures to manage the condition.
Addressing Postnatal Transmission Concerns
Parents often worry about spreading the virus to their infant through close, everyday contact after birth. Fortunately, HPV is not typically transmitted through casual contact, such as hugging, kissing, or sharing household items. The virus requires skin-to-skin contact, generally involving the genital or oral mucosa. Therefore, the risk of transmitting HPV through normal parental care and interaction is negligible.
Concerns about passing the virus through breast milk are common among new mothers with HPV. Research has consistently shown that breastfeeding is safe, and the benefits far outweigh the unlikely risk of transmission. While HPV DNA has been detected in a small percentage of breast milk samples, studies found that infants exposed to this milk did not contract the virus. No major health organization recommends against breastfeeding due to a maternal HPV infection.
Prevention and Management Strategies
The most effective strategy to prevent HPV infection and associated risks in a child is proactive health management before and during pregnancy. The HPV vaccine is highly effective against high-risk types and the low-risk types 6 and 11, which cause genital warts and RRP. Vaccination is recommended for individuals up to age 45 who were not previously vaccinated. Completing the series before pregnancy provides protection for both the parent and potentially the child.
Pregnant individuals should continue routine cervical screening, such as Pap or HPV tests, as directed by their healthcare provider. If genital warts are present, they may be monitored or treated during pregnancy, often using cryotherapy (freezing) or surgical removal, especially if they are large or obstruct the birth canal. The decision to remove warts is typically done after the first trimester to prevent potential transmission.
The mode of delivery is a point of discussion, but Cesarean section is not routinely recommended solely to prevent HPV transmission. While a C-section can reduce transmission risk compared to vaginal delivery, the absolute risk of the child developing RRP is so low that the risks of major surgery usually do not justify the procedure. Healthcare providers weigh individual circumstances, such as the size and location of any lesions, when making a delivery recommendation. Expectant parents should maintain open communication with their obstetrician to discuss their HPV status and the most appropriate management plan.