Getting the HPV vaccine before pregnancy was linked to lower odds of preterm birth, a large Swedish study found. The study was published in the BMJ, Pulse and News-Medical reported.

Researchers looked at 624,713 first births to women aged 16 to 35 in Sweden from 2006 to 2023, Pulse reported. About 15% of the women had received the HPV vaccine before pregnancy. The vaccine protects against a virus that can cause cervical cancer.

Overall, vaccination was linked to lower odds of all the pregnancy problems the team studied. But only some results were strong enough to count as significant. The odds were 5% lower for preterm birth and 15% lower for very preterm birth, News-Medical reported.

The link was stronger in women vaccinated before age 17. They had 10% lower odds of preterm birth and 11% lower odds of spontaneous preterm birth, News-Medical reported.

The authors said HPV infection, and treatment for cervical lesions caused by HPV, have been tied to preterm birth. The vaccine "may also confer additional benefits by reducing the risk of adverse events," they wrote, Pulse reported.

The study looked back at records. It does not prove the vaccine caused the lower risk. Some results grew weaker when the team took past cervical lesions into account, News-Medical reported. Results from other countries have been mixed. A Scottish study found no link with preterm birth.

Each woman with a pregnancy problem was compared with up to 10 women who did not have one. The team adjusted for smoking, body weight and other factors.

What we know: In Sweden, women vaccinated against HPV before pregnancy had somewhat lower odds of preterm birth, especially if vaccinated young.
What we don't: Whether the vaccine itself lowers the risk, and how much other factors explain the link.