CDC guidelines recommend flu vaccination of all women who will be pregnant during flu season, regardless of trimester. Only inactivated virus administered via an injection should be used (NOT live attenuated influenza virus or nasal spray vaccine).
CDC guidelines recommend vaccination with tetanus and diphtheria as needed during pregnancy. In place of tetanus and diphtheria, vaccination with tetanus, diphtheria and Pertussis (whooping cough) may be substituted. Pertussis which is very contagious can cause serious illness, especially in infants too young to be fully vaccinated. Either vaccine may be administered during the second or third trimester of pregnancy.