Can a tetanus shot cause complications during the first trimester...?

Tetanus shot. While conventional doctors would say that a tetanus shot is "safe" during pregnancy, any vaccine can potentially cause harm during pregnancy. ... In fact, every vaccine has the potential for serious side effects in any age, from birth through death!
Unlikely. A tetanus shot or specificly tdap, is actually encouraged in pregnancy as a way to assure baby has protective antibodies at birth. Many will time an optional dose after the first trimenter when organogenisis is complete to avoid its implication in the few but predictable pregnancies that have random unrelated problems.