There are a few things you can do to remove period stain from a car seat. The first is to use a mild soap and water solution to clean the area. This will help remove any built-up bacteria that may have been on the fabric. Next, use a dry cloth to gently rub the stain away. Be careful not to damage the fabric too much. Finally, use a vacuum cleaner and bucket to suck up all of the excess liquid that has been released from the seat. This will help remove all of the period stains from the fabric.