It's different for everyone, but I think the rule of thumb is as long and the BR is over 120 your good to go. Mine at 6w was 126, 7w 151, 8w 172, 9w 178 & 181, 10w 174, 11w 169, 12w 161. I havent had them tell me since. But, I do know around 11-13 weeks the HR starts to drop. In 3 weeks I'll find out what she'll be at 20.5 weeks.