HPV vaccine before pregnancy tied to fewer adverse pregnancy outcomes

Quadrivalent human papillomavirus (qHPV) vaccination before pregnancy was associated with lower odds of preterm birth and several other adverse pregnancy outcomes, with stronger associations among women vaccinated at younger ages, according to a nationwide Swedish registry study published October 7, 2026, in BMJ.

Preterm birth is one of the leading global causes of newborn mortality and a major contributor to medical and social impairment in adulthood, yet effective prevention and treatment options remain limited. Persistent infection with high-risk HPV is the primary cause of cervical precancer and cancer, and emerging evidence has linked HPV infection to adverse pregnancy outcomes, including preterm birth.

Excisional cervical treatments, commonly performed for HPV-related high-grade lesions and early-stage cervical cancer, have also been shown to increase the risk of adverse pregnancy outcomes. Because these lesions and treatments often occur during reproductive years, the investigators noted that HPV may be an important and potentially preventable contributor to preterm birth.

Evaluating HPV vaccination and pregnancy outcomes

Earlier data from Denmark, Australia, Finland, and Scotland suggested HPV vaccination before pregnancy may be associated with reduced risk of some adverse pregnancy outcomes. However, those studies often lacked nationwide data with individual-level linkage for detailed confounder control and frequently examined outcomes in isolation, the study authors noted.

To address these gaps, they used population-based Swedish registers to analyze 624,713 singleton births among nulliparous women aged 16 to 35 years between 2006 and 2023. Of these women, 92,620 (14.8%) had received qHPV vaccination before pregnancy.

Sweden introduced its first HPV vaccine in 2006, began offering subsidized vaccination to girls aged 13 to 17 years in 2007, and launched a free school-based program for girls aged 10 to 12 years in 2012, alongside catch-up vaccination for girls born from 1993 to 1998.

Primary outcomes were preterm birth before 37 weeks, including its subtypes, and spontaneous preterm birth. Secondary outcomes included preterm prelabor rupture of membranes (PPROM), prelabor rupture of membranes, small for gestational age (SGA) infant below the 10th percentile, severe SGA infant below the 3rd percentile, stillbirth, and neonatal mortality. Conditional logistic regression was used to estimate adjusted odds ratios (aORs), and effect modification by age at vaccination was assessed.

Which adverse pregnancy outcomes were lower after qHPV vaccination?

After adjustment for confounders, qHPV vaccination was associated with lower odds of all included adverse pregnancy outcomes. Statistically significant associations were observed for:

• Preterm birth (aOR, 0.95; 95% CI, 0.91-0.99)
  Very preterm birth at 28 to 31 weeks (aOR, 0.85; 95% CI, 0.75-0.97)
• Spontaneous preterm birth (aOR, 0.95; 95% CI, 0.91-0.99), PPROM (aOR, 0.93; 95% CI, 0.87-1.00)
• Severe SGA infant (aOR, 0.92; 95% CI, 0.87-0.97)

Risk reductions were generally more pronounced among women vaccinated at younger ages, in line with prior evidence that HPV vaccination offers stronger protection against infection, precancer, and cancer when given earlier.

What do the findings mean for HPV vaccination programs?

A large share of HPV vaccine doses worldwide are delivered to school-aged girls through routine programs, and the investigators noted that even modest reproductive benefits could translate into substantial population-level health gains.

According to the authors, the findings extend the benefits of HPV vaccination beyond cancer prevention and further strengthen its clinical and public health value.

Reference:

Zhang Z, Ploner A, Sengpiel V, et al. Quadrivalent human papillomavirus vaccination before pregnancy and pregnancy outcomes: nationwide, population based case-control study. BMJ. Published online October 7, 2026. Accessed October 9, 2026. https://doi.org/10.1136/bmj-2026-100739