Yes, Tetanus Toxoid does contain Thimerosal (mercury), in most vaccines. For more info: http://www.vaccinesafety.edu/thi-table.htm BUT, there are several tetanus vaccines that are free of mercury....
Tetanus toxoid is what a tetanus vaccine contains. You're body will make anti-bodies to tetanus once given the tetanus vaccine, offering you protection for "up to" 10 years from the bacterial disease...
According to the CDC's Vaccine Information Statement, it is best to be vaccinated as soon as possible after giving birth if you have never received the vaccine. If there is a need for the tetanus...