Dr Q- checking in again

Dr Q- I know that with any pregnancy there is a miscarriage rate of about 30%. Does this percentage, decline, however, with age? For example, I am only 31 so would my chance of miscarrying be lower than someone who is 35 or older? Also, how possible is it for things to be going fine and then for the baby to die in utero within the first 3 months and not know it? I still don't have any signs of pregnancy (except that my belly already looks like I am 4 months!) and I am 6 weeks pregnant. Does it look good for me the fact that I am 6 weeks pregnant and all my HCG's have looked good thus far. A beta of 39 on 12 DPO, 105, 14 DPO, 485 17 DPO, 1163 20 DPO and 6741 25 DPO? As always, thanks for your advice.