For a study, researchers sought to see if the Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention recommended influenza and tetanus toxoid, decreased diphtheria toxoid, and acellular pertussis (Tdap) immunizations in pregnancy were linked to an increased risk of stillbirth. From January 1, 2012, to September 30, 2015, researchers compared the odds of vaccination in pregnancies that ended in stillbirth (defined as a fetal loss at or after 20 weeks of gestation) versus those that ended in a live birth in the Vaccine Safety Datalink, which was matched 1:4 on-site, month, and year of last menstrual period. Patients with singleton pregnancies that terminated in stillbirth or live delivery and who had at least one prenatal visit, pregnancy date information, and continuous health plan membership for the course of the pregnancy were included in the study. All stillbirth medical records were examined. When examining the link between influenza or Tdap vaccination and stillbirth, we have statistical power to detect an odds ratio (OR) of 1.37. Between 2007 and 2015, they looked at stillbirth rates in pregnant patients aged 14–49 years in the Vaccine Safety Datalink.
There was no significant association between influenza vaccination during pregnancy and stillbirth (343/795 [43.1%] stillbirths in the case group vs 1,407/3,180 [44.3%] live births in the control group, OR 0.94, adjusted OR 0.95, 95% CI 0.79–1.14, P=.54) in the matched analysis of 795 confirmed stillbirths in the case group and 3,180 live births in the control group. Tdap vaccination during pregnancy had no significant connection with stillbirth (184/795 [23.1%] stillbirths in the case group versus 746/3,180 [23.5%] live births in the control group, OR 0.97, aOR 0.96, 95% CI 0.76–1.28, P=.91). The stillbirth rate in the Vaccine Safety Datalink was 5.2 per 1,000 live births and stillbirths from 2007 to 2015. There was no link discovered between prenatal immunization and the risk of stillbirth. These data confirm the ACIP guidelines for prenatal vaccination.
