From the Journals

Exposure to HPV vaccine in pregnancy not linked to birth defects

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Safety of HPV vaccines upheld

Although a large number of women (1,665) were immunized in the first trimester of pregnancy, when organogenesis occurs, their offspring did not have a significantly higher rate of major birth defects compared with offspring born to unvaccinated women. The numbers of spontaneous abortions, preterm births, infants with low birth weight, infants who were small for gestational age, and stillbirths were not higher in the vaccinated cohorts than in the unvaccinated cohorts, although the number of stillbirths was small.

Dr. Kathryn M. Edwards of Vanderbilt University, Nashville, Tenn. Courtesy Susan Urmy, Vanderbilt University

Dr. Kathryn M. Edwards

These data are very encouraging and strongly support the safety of HPV vaccines if they are inadvertently given in pregnancy, a finding that complements previous safety reports of HPV vaccine in nonpregnant women. These data also show that adverse outcomes occur at a baseline rate in pregnancy and that when no control group is included in studies, these outcomes may be inappropriately attributed to the vaccine.

Kathryn M. Edwards, MD, is in the division of infectious diseases and the department of pediatrics at Vanderbilt University, Nashville, Tenn. She reported receiving grants from Novartis for research on group B strep vaccines in pregnancy. These comments are excerpted from an accompanying editorial (N Engl J Med. 2017;376[13]:1280-2).


The quadrivalent human papillomavirus (HPV) vaccine was not associated with any adverse pregnancy outcomes when inadvertently given during pregnancy, according to the findings from a nationwide Danish study.

“Our results are consistent with other evidence that does not indicate that the vaccination of pregnant women with inactivated virus, bacterial, or toxoid vaccines generally confers a higher risk of adverse pregnancy outcomes than no such vaccination. Our results also confirm and considerably expand on results from previous studies of the quadrivalent HPV vaccine,” wrote Nikolai M. Scheller, MD, of the Statens Serum Institut, Copenhagen, and his colleagues.

vaccine jarun011/Thinkstock
HPV vaccination is not recommended during pregnancy, but a number of women are inadvertently vaccinated early in unplanned or unrecognized pregnancies. To assess the safety of the vaccine in such patients, the investigators analyzed data in nationwide registries for 581,550 singleton pregnancies during a 7-year period, including 1,665 pregnancies in which the mother was vaccinated at 0-12 weeks’ gestation. These cases were propensity matched with four controls each, and pregnancy outcomes were compared.

Quadrivalent HPV vaccination was not associated with any increase in risk for major birth defects (prevalence odds ratio, 1.19), spontaneous abortion (hazard ratio, 0.71), preterm birth (prevalence OR, 1.15), small size for gestational age (prevalence OR, 0.86), or low birth weight (prevalence OR, 1.10). It also was not associated with increased risk for stillbirth, but this outcome occurred in only two case patients and four controls, making it “impossible to draw clinically meaningful conclusions” regarding the risk for stillbirth, Dr. Scheller and his colleagues reported (N Engl J Med. 2017;376[13]:1223-33).

“Because many [adverse] pregnancy outcomes are rare, our study did not have the statistical power to assess the risks of stillbirth and specific major birth defects associated with quadrivalent HPV vaccination. Larger studies would be needed to address these outcomes,” they added.

Novo Nordisk and the Danish Medical Research Council funded the study. Dr. Scheller reported having no relevant financial disclosures; two of his coauthors reported receiving research grants from the Novo Nordisk Foundation and the Danish Medical Research Council.

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