Maternal Tdap Vaccination Does Not Affect Baby’s Growth: Study

A new study published in the journal of Vaccine showed that there was no correlation between variations in newborn development and maternal tetanus, diphtheria, pertussis (Tdap) immunization either during pregnancy or after delivery. Infant development and healthcare usage after prenatal Tdap immunization are not well documented. Thus, this study evaluated the effects of the Tdap vaccine on baby development and healthcare utilization during pregnancy or when administered to nursing mothers.

Using electronic health information from two US healthcare systems, this study included were prenatal care patients with a singleton live birth (2014–2022) and their associated babies. The pregnancy analyses were used to compare the results of infants who got the Tdap vaccine at ≥27 gestational weeks with those who did not, up to 90 days after birth. They evaluated Tdap vaccination within 90 days of birth against no immunization for postpartum analyses, which were limited to human milk feeders.

Growth halting and sluggish weight gain (<5th percentile) were the infant growth outcomes evaluated between 3 and 12 months of age. Counts of outpatient visits, including well visits, and ED visits up to six months following birth were used to measure infant healthcare use outcomes; uninsured infants were not included. Researchers calculated 95% confidence intervals (CI) and adjusted prevalence ratios (aPR), also known as rate ratios (aRR).

Infant growth and healthcare utilization analyzes were available for 33,261 and 25,335 pregnancies, respectively. Tdap vaccination during pregnancy was marginally linked with the risk of outpatient visits (aRR: 1.07, 95% CI: 1.01-1.12), but not with growth faltering (aPR: 0.96, 95% CI: 0.85-1.09), slow weight gain (aPR: 0.93, 95% CI: 0.81-1.07), or ED visits (aRR: 1.00, 95% CI: 0.84-1.18). The 3034 and 3191 nursing participants who qualified for the infant development and healthcare utilization analyzes, respectively, showed no correlations.

Overall, the study offers empirical proof that the perinatal Tdap vaccine is safe. A higher risk of unfavorable development outcomes was not linked to Tdap immunization during pregnancy or breastfeeding. It was not possible to rule out residual confounding by health-seeking behavior, even though Tdap vaccination during pregnancy was linked to a modest increase in outpatient visits per baby. Additionally, there was no correlation between prenatal Tdap immunization and baby ER visits. 

Reference: 

Palmsten, K., Cao, J., Vazquez-Benitez, G., Ehresmann, K., Seburg, E. M., Kharbanda, E. O., Clark, L. R., Li, L., & Daida, Y. (2026). Assessment of infant growth and health care utilization following tetanus, diphtheria, pertussis (Tdap) vaccination during pregnancy and lactation. Vaccine, 92(129123), 129123. https://doi.org/10.1016/j.vaccine.2026.129123