The human papillomavirus (HPV) is an organism that is transmitted by skin-to-skin contact and frequently by vaginal, anal or oral sex. The American Centers for Disease Control and Prevention (CDC) identifies HPV as the most prevalent sexually transmitted infection and suggests that most people who are sexually active will contract some variety of the virus at some stage of their lives (CDC, 2017). There are more than 150 varieties of the HPV and, of those, 40 are known to be transmitted through sexual contact. The virus can affect a person's genitals, anal area, mouth or throat, so intercourse is not necessary for an infection to be passed on.
Depending on the type or strain of HPV, the infection can cause warts on and around the genitals or a range of different cancers. In women it can cause cervical and ovarian cancer. In both men and women, it can cause anal and oropharyngeal cancers. Fortunately, not all HPV infections cause warts or cancer and most infections will resolve by themselves with help from the body's own immune system; however, a person can carry an HPV infection without showing symptoms and can pass the virus on to sexual partners without knowing it.
If the immune system is not able to overcome the infection, the virus can lead to significant health issues. Approximately 70% of cervical cancers are caused by types 16 and 18 of the HPV virus, while around 90% of genital warts are caused by types 6 and 11. As people can carry one or multiple types of the virus at the same time, a comprehensive screening test is the best way to know if a person is at risk.
The NHS now offers all girls aged 12–18 years old a free course of vaccines against the most common types of HPV. The vaccine that is used offers protection from HPV types 16 and 18 and types 6 and 11. The vaccine is highly effective at preventing girls from contracting the types of virus that cause the majority of cases of cervical cancer and genital warts.
Testing for HPV
There is no HPV test that can be carried out on a blood sample. However, it is possible to carry out an HPV test on a sample of cells from the cervix or from a swab of the inside of the vagina. If there are visible warts or lesions in the genital areas, these too can be swabbed and tested for HPV. In the UK, genital HPV testing is now included in the cervical screening programme that is offered to all women aged 25–64 years.
If a woman has had an abnormal cervical screening result in the past, she may need to have a smear test while she is pregnant, and this will likely not interfere with the pregnancy. If this is required, the smear test will usually be performed in weeks 13-26. However, if a woman is due for a smear test while she is pregnant but her previous tests have been normal, then the test will often be delayed until at least 3 months after birth. This is because smear tests are more difficult to interpret during pregnancy due to cell changes caused by hormonal factors.
What implications does HPV have for pregnancy?
There has been a great deal of research conducted to establish any links between an HPV infection and alterations to fertility and whether and HPV infection can compromise a pregnancy.
A number of studies have concluded that there is no clear link between an HPV infection and reduced fertility or risks to a pregnancy (Skoczynski et al, 2011; Souho et al, 2015; Xiong et al, 2018). Other studies, however, have found connections between HPV infections in both men and women and difficulties in conceiving and carrying a pregnancy to full term (Gomez et al, 2008; Garolla et al, 2011; Pererira et al, 2015).
One such study (Pereira et al, 2015) has shown a wide range of factors linked to HPV infection that could affect a couple's ability to conceive and carry a pregnancy to term. The study concluded that HPV infection could lead to sperm cell death, reduced sperm count, reduced sperm motility, alterations to the sperm shape, death of embryonic cells, miscarriages and premature rupture of membranes.
Infection with certain types of HPV is therefore likely to be a risk factor for reduced fertility or infertility. Detecting any underlying HPV infection in both men and women before they try to conceive a child would seem highly advisable. Once the infection has cleared, fertility should increase, and the risk of preterm birth, miscarriage and infection of the newborn will be reduced.
There are many services offering smear tests and the results of these tests may not be automatically shared with the patient's doctor. It is important that any positive HPV or smear test result be communicated to a qualified doctor to enable appropriate follow up, whether for further testing or referral for colposcopy. Doctors are likely to want to monitor a woman with a positive HPV or smear test closely because pregnancy can be associated with more rapid cell changes. If cervical cell changes do occur during pregnancy, then it is preferable to delay any treatment until after birth because there could be a risk of haemorrhage (Public Health England and NHS, 2016). If a woman is receiving treatment for genital warts, her doctor may suggest stopping treatment for the duration of the pregnancy (GP Notebook, 2016).
In cases where a woman has genital warts present during pregnancy, then the size of these will be measured and monitored. The hormone changes that occur during pregnancy can cause warts to grow larger, multiply or potentially bleed. It is preferable for wart treatment to be delayed until after birth, but if the warts grow so large that there is a danger of obstructing the vagina, then they may need to be removed before birth. Wart removal may involve surgery, chemical treatment or freezing the tissue.
HPV and birth
Even if a woman has an active HPV infection during pregnancy, the risk of transmitting it to the baby during birth is very low. In the unlikely event that an infection is transmitted, then there is a high probability that the baby's body will be able to clear the virus on its own.
There is a very small possibility that a baby whose mother has genital warts might develop warts in his or her throat. This condition is called respiratory papillomatosis and can potentially be very serious as there is a risk that the warts could block the baby's throat. The baby may need laser surgery in order to protect their ability to breathe, which may be required anywhere from monthly to biannually. Before the age of 3 a patient may have frequent recurrences so may require multiple surgeries (The Children's Hospital of Philadelphia, 2019).
HPV after birth
If doctors have been monitoring an HPV infection during pregnancy, then they will continue to do so after birth. In most cases, the infection will clear up without treatment and any genital warts will also disappear over time.