Pregnant women infected with certain strains of human papillomavirus, or HPV, may have an increased risk of preterm labor, a new study suggests.
HPV is a sexually transmitted disease that can cause genital warts. Most of the time, the immune system clears the infection.
But some strains of HPV become persistent in a minority of people and, over time, can lead to certain cancers.
In fact, almost all cervical cancer in the United States is caused by a persistent HPV infection, according to the United States Centers for Disease Control and Prevention. And two strains of HPV – known as 16 and 18 – are responsible for most.
Now the new study, published online this month in the journal JAMA network open, connects the two strains to premature birth.
Researchers found that out of 899 pregnant women, those infected with the strains throughout pregnancy were almost four times more likely to give birth prematurely than uninfected women. Premature births occur before the 37th week of pregnancy.
The results do not prove cause and effect, said lead researcher Helen Trottier, assistant professor at the University of Montreal in Canada.
There could be other explanations for the link between high-risk HPV and premature birth, according to Trottier.
Her team explained as many alternative explanations as they could, including women’s smoking and drinking habits, their age and education level, and whether they had high blood pressure or diabetes. related to pregnancy.
But persistent infection with HPV-16/18 was still, in itself, a risk factor for preterm delivery.
“It may be that the problem is specifically related to HPV-16 and -18,” Trottier said. That wouldn’t be surprising, she added, as these are the variants that most often cause damage to the cervix.
This raises another question, however: When the Pap test for cervical cancer detects a more serious cervical injury, doctors may remove the abnormal cells. It is therefore possible that treatment, which changes the cervix, may explain the link between high-risk HPV and preterm delivery.
Trottier’s team couldn’t find any evidence of this, however: the link was just as strong in women with no history of cervical treatment, they found.
Still, more research is needed to understand what is going on, according to Trottier. “This is the first study to show this,” she said. “We need more studies to confirm the finding.”
HPV is the most common sexually transmitted disease in the world – so common that almost all sexually active people will contract the virus if they don’t get the HPV vaccine, according to the CDC.
The new results illustrate this. Of the 899 pregnant women involved, 42% tested positive for HPV in their first trimester, and most of the infection persisted until the third trimester. There is no treatment that eradicates the virus, Trottier noted.
About 7% of the women harbored the HPV-16 or -18 strains, according to the report.
In the end, 55 women gave birth prematurely. At first glance, there was no connection between preterm delivery and HPV infection. But when researchers focused on the type of HPV, the picture changed.
Women with persistent HPV-16 or -18 infection were 3.7 times more likely to give birth early than women without HPV infection in the first and third trimesters.
Dr. Joy Baker is an obstetrician / gynecologist and spokesperson for the non-profit organization March of Dimes.
She called the new findings “very interesting”. Some sexually transmitted infections are known to be associated with premature birth, Baker said, namely bacterial infections that can cause irritation to the cervix. But HPV, a viral infection, has not been on the radar.
Baker said it would be important for future studies to confirm this finding.
If the HPV strains contribute to preterm labor, Trottier said, it would be essential, in part because infection can be prevented with the HPV vaccine.
In the United States, the vaccine is recommended for girls, as young as 9 and under 12. It is also recommended for boys, as HPV can cause penile, anal, and throat cancer.
For now, Baker has said that there are some established and modifiable risk factors for preterm birth, including being underweight or overweight before pregnancy, or high blood pressure or diabetes before or during pregnancy. pregnancy.
Another contributor, Baker noted, has a short interval between pregnancies. It is recommended that women wait 12 to 18 months after childbirth before becoming pregnant again.
Early prenatal care is essential, she added. But ideally, women should see their doctor when planning a pregnancy to get a checkup.
“Take time for these preventative visits,” Baker said. “Learn about your health and try to plan for your reproductive life.”
The March of Dimes has more on premature birth.
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