A study of women who received a tetanus, diphtheria, acellular pertussis (Tdap) vaccination during pregnancy found no increase in risk that their children would later be diagnosed with autism spectrum disorder.

The study, “Prenatal Tetanus, Diphtheria, Acellular Pertussis Vaccination and Autism Spectrum Disorder,” will be published in the September 2018 issue of Pediatrics, published online Aug. 13.

Researchers reviewed the records of 81,993 pairs of diverse pregnant women and their children who were born between Jan. 1, 2011, and Dec. 31, 2014, at Kaiser Permanente Southern California hospitals. Following up with the mother-child pairs, they identified children who had been diagnosed with autism spectrum disorder after age 1 through June 30, 2017.

The incidence rate of autism spectrum disorder was 3.78 per 1,000 people in the Tdap-vaccinated group. The rate of autism spectrum disorder was 4.05 per 1,000 in the unvaccinated group. The Tdap vaccine has been shown in prior research as effective in protecting young infants from pertussis, which has risen in incidence in the past decade.

Evidence showed that antibodies are passed along to newborns and that the vaccine was 91.4% effective in providing some immunity until newborns reached 2 months of age.