yorkies in heat

Question
how long are they in heat mine has been going for at least 7 days now . thank you

Answer
Hi Glenda,
 Females stay in heat for about 21 days...they are generally receptive to males from the 10th 'til the 16th day. That is when they are ovulating and can be bred to be become pregnant. There are few a very exceptions to the rule but this an average for females.