New England Journal of Medicine
March 30, 2017  Vol. 376 No. 13
http://www.nejm.org/toc/nejm/medical-journal

Editorial
Ensuring Vaccine Safety in Pregnant Women
Kathryn M. Edwards, M.D.
N Engl J Med 2017; 376:1280-1282 March 30, 2017 DOI: 10.1056/NEJMe1701337
[Initial text]
In this issue of the Journal, investigators from Denmark present a comprehensive review of the adverse pregnancy outcomes encountered in women who received quadrivalent human papillomavirus (HPV) vaccine during pregnancy, as compared with those who did not.1 The investigators assembled data on all the pregnancies in Denmark that occurred within a 7-year period, and they used nationwide registries to identify the dates of pregnancy, pregnancy outcomes, and maternal characteristics, including receipt of HPV vaccine and dates of vaccine administration. Vaccinated women and unvaccinated women were propensity-score matched in a 1:4 ratio, and pregnancy outcomes were compared.