Pregnancy and infant outcomes in the clinical trials of a human papillomavirus type 6/11/16/18 vaccine: a combined analysis of five randomized controlled trials

Obstet Gynecol. 2009 Dec;114(6):1179-1188. doi: 10.1097/AOG.0b013e3181c2ca21.


Objective: To present a combined analysis of the pregnancy outcomes for women aged up to 45 years enrolled in five phase III clinical studies of the prophylactic quadrivalent human papillomavirus 6/11/16/18 vaccine.

Methods: Twenty thousand five hundred fifty-one women aged 15-45 years received quadrivalent HPV vaccine or placebo at day 1 and months 2 and 6. Urine pregnancy tests were performed immediately before each injection; participants testing positive were not vaccinated. Women who became pregnant after enrollment were discontinued from further vaccination until resolution of pregnancy. All pregnancies were followed for outcomes.

Results: During the studies, 1,796 vaccine and 1,824 placebo recipients became pregnant, resulting in 2,008 and 2,029 pregnancies with known outcomes. No significant differences were noted overall for the proportions of pregnancies resulting in live birth, fetal loss, or spontaneous abortion. A total of 40 neonates born to vaccinated women and 30 neonates born to women given placebo had one or more congenital anomalies (P=.20). The anomalies were diverse and consistent with those most commonly observed in the general population. The vaccine was well tolerated among women who became pregnant.

Conclusion: Administration of quadrivalent human papillomavirus vaccine to women who became pregnant during the phase III clinical trials did not appear to negatively affect pregnancy outcomes. The vaccine is a U.S. Food and Drug Administration pregnancy category B medication (animal studies revealed no evidence of fetal harm, but there are no adequate and well-controlled studies in pregnant women); however, vaccination is not recommended during pregnancy. Postlicensure surveillance is ongoing.

Clinical trial registration:,, NCT00092521, NCT00092534, NCT00092495, NCT00092547 and NCT00090220.

Level of evidence: II.

MeSH terms

  • Adolescent
  • Adult
  • Clinical Trials, Phase III as Topic
  • Female
  • Human Papillomavirus Recombinant Vaccine Quadrivalent, Types 6, 11, 16, 18
  • Humans
  • Infant, Newborn
  • Infant, Newborn, Diseases / chemically induced*
  • Lactation
  • Middle Aged
  • Papillomavirus Vaccines / administration & dosage
  • Papillomavirus Vaccines / adverse effects*
  • Pregnancy
  • Pregnancy Outcome*
  • Randomized Controlled Trials as Topic
  • Young Adult


  • Human Papillomavirus Recombinant Vaccine Quadrivalent, Types 6, 11, 16, 18
  • Papillomavirus Vaccines

Associated data