During pregnancy most women receive Tetanus injections but with 3-in-1 vaccination, expecting mothers can receive protection against 3 diseases: Tetanus, Diphtheria & Pertussis - all three together. Tetanus is a nerve disease; Diphtheria is a serious throat infection that can block airways; And Pertussis is a contagious respiratory disease which can lead to hospitalisation in infants aged under 2 months.