Yes I was classed as high risk - because of my age and because I had had my second child very quickly and I had my third at home accidentally. Also, one of the things was much bigger than the other. It just means they will keep a closer eye on you, which is good.
I am super-anti the 'twin' word as I am a twin - I go out of my way to ensure that my children are never called 'twins' by anyone and that they are treated as individuals (I'm a little bit mental about it - I even have an internal party invitation policy!).
Please ask if you think there's anything I can help you out with - my kids are now 14, 11, 9 and 2 x 7 year olds. It was hard but it's not for ever (and sleep is overrated), x