I decided against doing it after talking with my midwife. There is such a wide range of numbers, that if its on the end of that number, some women just worry about how "low" the number is when its still in the healthy range. And then if it only SLIGHTLY doubles, there is another freak out, even though just doubling or barely doubling is still okay.
I learned the hard way that worrying doesn't change anything. I think its only worth putting yourself through the worry if something is going wrong (spotting, loss of symptoms). So I opted just to tough it out a few more weeks and go in for an ultrasound at 8 weeks.
I'm not trying to be mean or opinionated - I just hate seeing women go and get beta's done just because they can and then the end up worrying for a whole week...when everything ends up fine. And just by waiting another 2 weeks, they can go get an ultrasound done and get a more definitive answer on how the little bean is doing by seeing that little heart flicker.