There has been an increase in the number of people with pertussis (whooping cough) over the past decade. This is attributed to a natural waning of immunity and also to the presence of more unimmunized people. Infants younger than three months are at greatest risk of death from pertussis.
In January 2013, a new recommendation was made for all pregnant women. It is now recommended that ALL pregnant women between 27 and 36 weeks of gestation should receive one shot of Tdap regardless of previous vaccine status. (Tdap is tetanus toxoid, low dose diphtheria toxoid, and acellular pertussis vaccine).
Vaccination of the mother will significantly reduce the risk of exposure to pertussis in the newborn. Furthermore, there is felt to be spread of maternal antibodies across the placenta which would also help reduce.