Significantly higher concentrations of pertussis antibodies were measured at delivery in women who received Tdap during pregnancy vs postpartum ( eg , pertussis toxin antibodies : 51.0 EU/mL [ 95 % CI , 37.1-70 .1 ] and 9.1 EU/mL [ 95 % CI , 4.6-17 .8 ] , respectively ; P < .001 ) and in their infants at birth ( 68.8 EU/mL [ 95 % CI , 52.1-90 .8 ] and 14.0 EU/mL [ 95 % CI , 7.3-26 .9 ] , respectively ; P < .001 ) and at age 2 months ( 20.6 EU/mL [ 95 % CI , 14.4-29 .6 ] and 5.3 EU/mL [ 95 % CI , 3.0-9 .4 ] , respectively ; P < .001 ) .