Not to be the nay sayer-- but if you are going to lose your baby to miscarriage before your first appointment- there is very little that could be done for you anyway. I think early OB appointments are pretty pointless ( I actually think most OB appts. are pretty pointless)...just take prenatal vitamins, eat well, rest as much as you can.
Nothing that they find in your blood work will be an issue immediately..and many OB offices wait until around 20 weeks to order blood panels.
I think it can be a huge, enormous hassle to see a different caregiver than the one who will be your primary caregiver- you have to deal with transferring all the records, and give your medical history a bazillion times...and all so they can tell you to take pre natal vitamins.
Do a little research about warning signs in the first trimester....and my opinion is that waiting until 15 weeks will be no different from having seen your midwife at 8 weeks or whatever. Most midwife practices aren't going to be doing early sonograms anyway as a routine procedure...
Personally - I don't think you are endangering your baby's health, there's nothing that they could do for your baby at this point anyway. Taking care of yourself is the absolute best way to care care of your baby
Praying for your peace of mind!