Hi there,
LAF try not to freak out about the 'high-risk' classification. It can be triggered by lots of different things - high BMI is one, as it increases risk for developing gestational diabetes, so you'll probably be offered a glucose tolerance test to check for it at some stage (not all pg women have this). Your history of recurrent MC and diagnosis of increased clotting factor during pg is another reason - they'll want to ensure that the placenta continues to work efficiently throughout the pregnancy so you may have more scans after the 20 week one to check growth/blood flow (again, most women wouldn't after 20 weeks).
You may also be referred to have an anaesthetic review, as they'll want to put a plan in for what happens if you're hospitalised for any reason or any impact the clotting stuff might have on anaesthesia. It probably won't have any at all, but it's best to have notes about this etc.
The 'high-risk' applies to your care during pregnancy, not necessarily during birth. So along with your normal antenatal check-ups which will probably still be done by midwives either at a local health-centre/surestart centre/hospital, you'll get a couple of appointments with an obstetrician who will review everything to ensure things are progressing normally and schedule the extra things if necessary. Most likely, you'll get a review at about 37 weeks (i.e. once you reach 'term') to discuss the birth and if everything's looking hunky-dory you'll be able to choose the MW-led suite. At my hospital, there was only one labour section and it was MW-led as a default, they just called OBs if the birth looked like it was moving away from 'normal' progress. There's not much point in worrying about the birth until you reach term anyway, as if things kick-off before that you're premature and automatically need hospital help, and until 37 weeks things like breech position, etc, are still likely to change.
It's not going to be related to previous AD use.
(I was on high-risk for DS due to high BMI and history of PCOS, it doesn't take much!)
p.s. don't feel bad about the BMI, mine is likely to be worse, I was weighed after my scan last week and just about cried when I saw the number. I'm as heavy now as I was during my pg with DS.
My vote is for 13+1 being the start of the 2nd trimester, which is the 14th Week 
digi so pleased for another good scan and for graduating! Do St M's graduate everyone after 10 weeks or is it based on your particular history?
So a booking in appointment - the holy grail! This means you'll get your handheld notes, doesn't it? Goodness, how real. Lovely quick HB and making up the days is great (and also quite reassuring for those of us following, nice to know that a few days variation can change quite quickly).
moomin fingers crossed it's just the placenta digging in and bleeding a bit while it does it.
boodle good news that it's not ectopic, that's hurdle 1 jumped. Hope you see some progress on Friday that reassures you.
Hello LimeFlower mmm, your name makes my quease disappear, so lovely and refreshing . Tooooooonnnnnes of us are the wrong side of 35, you're in good company m'dear. I think it's traditional to get a stinking cold the moment you can't take anything for it. I recommend steam inhalations or saline nasal spray to help the blocky nose and lemon/honey/ginger drinks. Double plus is the ginger might help any nausea that starts to rear it's ugly head. I've been lurking on the May thread too, I tend not to join as have had to leave several times (this my 4th pg after 3MCs following DS), but I think I might be brave this time as there are several ladies on May with a history of MCs and it's not too ''oooooohhhhh, I'm having a bayyybbbeeeee " yet. takes cynical hat off and puts back in closet
googie you may as well hop off to the dr and let them know you're pg again. As LimeFlower said, if the worst does happen, it's on record, and there might be the possibility of an early scan which some people find reassuring. Heavy boobs and sickie burps count.
Livin I'm afraid I don't even know what the sacroli-thingy joint is? What sort of pain?
Well I'm off for a scan this afternoon (am in NZ for any confused about timing of this post). I'm not too worried about it, but can't help feeling that this could be the last time I see my bean alive. 
Oh, in other news - I went to the opera last night - very good for distraction on the night before a scan.
And I'm wearing those seabands for nausea and they seem to be helping. Which is nice.