Uki - I was the same as you last time, decided not to have an early scan, then had a mmc - only detected at dating scan at 13+1 - that was horrendous I'd had sickness (not as bad as this time, but still vomiting), constipation, exhaustion - the works ... so that's why I chose to have a scan this time - and why the midwife I saw was completely in favour of it. I just couldn't cope with the thought of having to wait 3 months to find out whether I really was pg, or just carrying around another mmc.
I'm 7 weeks today (by my dates) and saw the hb yesterday - bean was lying funny and appeared smaller than my estimate to sonographer, but she didn't give me a date, just said that everything was there and normal.
The knock-on effect is also that the midwife who referred me to EPAU asked me to phone her to let her know the result of the scan. She phoned me back today, and has booked me in for my booking appointment at home on Saturday.
I know there's still a lot that can go wrong - but at least I have seen my baby, and put my mind at rest.
ejt