No, there are no chances of getting pregnant if sperms are present on toilet chair. Sperms at the toilet chair or any place other than inside of female genitalia die immediately because of acidic pH. Only from the cervix of the ladies, alkaline pH starts and sperms can survive there. So, sperms can not go to inside you from the toilet chair. To get pregnant only ejaculate inside female body during fertile days is necessary.