Evaluation of the Association of Maternal Pertussis Vaccination With Obstetric Events and Birth Outcomes

IMPORTANCE: In 2010, due to a pertussis outbreak and neonatal deaths, the California Department of Health recommended that the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) be administered during pregnancy. Tdap is now recommended by the Advisory Committee on Immunization Practices for all pregnant women, preferably between 27 and 36 weeks’ gestation. Limited data exist on Tdap safety during pregnancy. OBJECTIVE: To evaluate whether maternal Tdap vaccination during pregnancy is associated with increased risks of adverse obstetric events or adverse birth outcomes. DESIGN AND SETTING: Retrospective, observational cohort study using administrative health care databases from 2 California Vaccine Safety Datalink sites. PARTICIPANTS AND EXPOSURES: Of 123 494 women with singleton pregnancies ending in a live birth between January 1, 2010, and November 15, 2012, 26 229 (21%) received Tdap during pregnancy and 97 265 did not. MAIN OUTCOMES AND MEASURES: Risks of small-for-gestational-age (SGA) births (