The question of which vaccines are safe during pregnancy is a very important one, and you should discuss it with your doctor
. Pregnant women are at high risk of becoming very sick with certain infections if they contract them during pregnancy, especially influenza. Also, unimmunized women may pass certain infections either to the developing baby or to the newborn after delivery.
However, at the same time, some vaccinations are not safe during pregnancy because they may cause harm to the developing baby. Therefore, it is always important to discuss the safety and necessity of each vaccine with your regular OB GYN doctor before proceeding.
Tdap is a vaccine which boosts immunity to three infections, tetanus, diphtheria, and pertussis. This vaccine is "inactivated" in that it doesn't contain any living organisms that cause the three types of infections. As such, it is safe during pregnancy and, in fact, it is recommended that all pregnant women receive this vaccines after the 20th week of pregnancy. Inactivated influenza is another vaccine that is strongly recommended in pregnant women.
On the other hand "live" vaccines should typically be given before or after pregnancy, but not during the pregnancy, because of the risks the may cause to the developing baby.
Talk to your OB GYN doctor for more information about this issue.