The benefits of the HPV vaccine may extend beyond protection against cancer. In a study published in The BMJ, researchers at Karolinska Institutet found that women who had been vaccinated against HPV were less likely to experience several pregnancy and childbirth complications, particularly preterm birth.
HPV (human papillomavirus) is the leading cause of cervical cancer. HPV infection and treatment of cervical cell changes have also been associated with an increased risk of certain pregnancy complications. A new study has investigated the link between the HPV vaccine and complications such as preterm birth, premature rupture of membranes, babies being small for their gestational age, stillbirth, and neonatal mortality.
The study is based on Swedish registers and covers 624,713 pregnancies among first-time mothers aged 16 to 35 between 2006 and 2023. 92,620 of these women had received the quadrivalent HPV vaccine prior to becoming pregnant, providing protection against four common types of HPV.
Stronger link when vaccinated at a younger age
Women who had been vaccinated before pregnancy consistently had a lower risk of the studied complications, particularly preterm birth. Compared with unvaccinated women, they were around five per cent less likely to give birth prematurely and around 15 per cent less likely to give birth very prematurely.
“We also observed that the associations were stronger among women who had been vaccinated before the age of 17,” says Zhongsong Zhang , doctoral student at the Department of Medical Epidemiology and Biostatistics , Karolinska Institutet. “This is consistent with previous findings that the HPV vaccine provides the best protection against HPV-related disease when administered at a younger age.”
A large register-based study
Although the researchers took into account several factors that could have influenced the results, as this was an observational study, it was not possible to conclude that the lower risk was caused by HPV vaccination. Nevertheless, the study covered a large number of women from the Swedish population over a long period of time.
“Even a relatively small reduction in the risk of preterm birth can be significant at a population level, given that HPV vaccination is administered to millions of young people worldwide,” says Jiayao Lei , assistant professor at the same department at Karolinska Institutet. “Our results suggest that the benefits of HPV vaccination may extend beyond cancer prevention to include the reduction of complications that can arise during pregnancy and childbirth.”
The study was carried out in collaboration with researchers at the University of Gothenburg, Sahlgrenska University Hospital and the Norwegian Institute of Public Health. Funding for the research came from the Swedish Research Council, the Swedish Research Council for Health, Working Life and Welfare, the Swedish Cancer Society, Karolinska Institutet and ALF grants, among others. See the scientific article for information on any conflicts of interest.
Publication
“Quadrivalent HPV vaccination before pregnancy and pregnancy outcomes: A nationwide, population-based case-control study” , Zhongsong Zhang, Alexander Ploner, Verena Sengpiel, Nestory Kasheshi, Bo Jacobsson, Joakim Dillner, Pär Sparén, Cecilia Kärrberg, Jiayao Lei, The BMJ, online 7 October 2026, doi: 10.1136/bmj-2026-100739.
