Women vaccinated against HPV before pregnancy had a slightly lower risk of giving birth early, a Swedish registry study has found. The researchers stress the study cannot prove the vaccine caused the difference, and catch-up vaccination and early antenatal care remain available to many women.
Swedish researchers studied 624,713 first pregnancies. Every mother was aged 16 to 35 and gave birth in Sweden between 2006 and 2023. Of them, 92,620 had received the quadrivalent HPV vaccine before pregnancy.
Those vaccinated women had about a 5% lower risk of preterm birth than unvaccinated women, the team reported in The BMJ on 7 October 2026. Their risk of very preterm birth was about 15% lower. The researchers came from Karolinska Institutet, the University of Gothenburg and Sahlgrenska University Hospital.
Stronger links for girls vaccinated before 17
Women vaccinated before the age of 17 showed stronger associations, the Karolinska Institutet release says. The team also looked at preterm rupture of membranes, babies small for gestational age, stillbirth and newborn deaths. Vaccinated women had lower risks for these outcomes too, the University of Gothenburg reported.
Jiayao Lei, an assistant professor at Karolinska Institutet, said: “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.”
An idea first tested in 2021
A 2021 Swedish registry study found that HPV infection near pregnancy was linked to a higher risk of preterm birth. The new work tested whether preventing infection might lower that risk. Verena Sengpiel, professor of obstetrics at the Sahlgrenska Academy, said the findings “are entirely consistent with the hypothesis we have been working from”.
One vaccine, one country, no proof of cause
The Swedish study is observational, so it shows an association. It cannot show the vaccine caused the lower risk, although the researchers adjusted for several factors that could affect the results. Cecilia Kärrberg, a senior consultant in obstetrics and gynaecology at Sahlgrenska University Hospital, said: “But this is an observational study, and we cannot establish a causal relationship.”
The study covered first-time mothers and one vaccine type only. Sweden has vaccinated girls against HPV since 2012. Further research will need to test whether the link holds for other vaccines and in other countries, and to explain how it might work.
13.4 million babies born early
About 13.4 million babies were born preterm in 2020, according to the latest available World Health Organization estimates. Preterm means before 37 completed weeks of pregnancy. Complications of preterm birth are the leading cause of death among children under five.
In low-income countries, half of babies born at or below 32 weeks die. In high-income countries, almost all of these babies survive. Preterm birth rates range from 4% to 16% of births across countries, and Lei noted that even small reductions in risk can add up across a population.
Catch-up vaccines and early antenatal care
HPV vaccination is the first pillar of WHO’s cervical cancer elimination strategy, which sets a target of 90% of girls vaccinated by 15 by 2030. Depending on the national schedule, it may be given as one or two doses.
In England, the NHS offers the HPV vaccine to all children aged 12 to 13. Girls who missed it can have it up to their 25th birthday, usually as a single dose, by asking a school nurse, school vaccination team or GP surgery. The NHS says there is no evidence the vaccine is harmful in pregnancy, although women may be advised to wait until after the birth.
WHO’s antenatal care guidelines include steps to help prevent preterm birth. They recommend at least eight contacts with health professionals during pregnancy, the first before 12 weeks, and an early ultrasound to date the pregnancy. For babies who do arrive early, WHO says kangaroo mother care, continuous skin-to-skin contact starting immediately after birth, can substantially reduce deaths.
This article is for information only and does not replace advice from a qualified health professional.
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