please help!!!

Hi all..my female chihuahua was having her first heat...i had her separated from my male chi..putting them in two different rooms...but that day while i was ***ping the floor..they mated ..would there be a chance of pregnancy? and what should i do if she's pregnant? i had no intention to breed them and wanted to steralize her when she's a year old..she's only 8 month plus now and my male is 10 month plus..please advise, thanks