Td vaccines is categorized as pregnancy category C.

(ZT)
Pregnancy is not a contraindication to Tdap (or Td) immunization. The AAP recommends that pregnant adolescents be given the same considerations for immunization as nonpregnant adolescents. If Tdap or Td vaccine is indicated, administration in the second or third trimester (before 36 weeks of gestation) is preferred, when feasible, to minimize a perception of an association of immunization with adverse pregnancy outcomes, which are more common during the first trimester. No evidence exists of a risk of immunizing pregnant women with inactivated bacterial vaccines or toxoids or inactivated viral vaccines ("Use of diphtheria," 2000). Both Tdap and Td vaccines are categorized as pregnancy category C agents by the Food and Drug Administration (FDA). FDA-acceptable well-controlled human studies and animal reproduction studies have not been conducted for Tdap (FDA, "Product approval information: Boostrix™ licensing action," "Product approval information: Adacel™ licensing action", 2005). Because of lack of data on use of Tdap vaccine in pregnant women, both Tdap manufacturers have established pregnancy registries for women immunized with Tdap during pregnancy. Health care professionals are encouraged to report Tdap immunization during pregnancy (Boostrix, GlaxoSmithKline Biologicals, 888-825-5249; or Adacel, Sanofi Pasteur, 800-822-2463).

http://www.guideline.gov/summary/summary.aspx?ss=15&doc_id=8816&nbr=4862