Does sound totally normal to me! Most pregnancies are detected at the 4 week mark by tests that pick up to 25 sensitivity, which is about right for 4 weeks, and if she's at 30+ that's right on target. More than that (because some pregnancies measure a little lower, mine did!) you want to see that number double about every other day. As long as it's doubling regularly, it can be a little low, and it's still perfectly normal! Has her ob determined the cause of her previous miscarriages? Sometimes there's an underlying health concern involved, or low progesterone, I wouldn't worry too much, as long as she's healthy, drinking lots of water and taking vitamins, it's really all you can do, and the rest is in God's hands. Congrats on the pregnancy, and I hope you both have a healthy and happy 9 months!