I took my nuvaring out for sex & didnt put it back in for 12 hours ... is there a possibility of pregnancy?

Cant do that: If Nuvaring has been out for more than 3 hours you can not reinsert the same one. You have to reinsert a new one. If you already reinserted the old one go ahead and remove it. You can not rely on Nuvaring for contraception if it has been out more than 3 hours. Use over the counter Plan B if intercourse was within 72 hours to decrease the risk of unplanned pregnancy.