Dannii, I think that you can look at this a number of ways and ultimately it is your personal decision what you do. They say it's ok to keep up a level of exercise similar to your pre pergnancy activity, so if you were pretty fit and active before getting pregnant then it's ok to keep it up - although you may feel you need to take it easy anyway. However it is hard to say what activities may be risky in terms of harming the baby. For me personally I was reasonably active previously - gym plus trained in martial arts pretty seriously. When TTC I told my instructor I wasn't going to do anything involving contact - esp sparring and now I am pg I've decided to only do very low impact stuff, do some teaching and pretty much not train till after 12 weeks and then I'll only do non contact stuff at a less intense level. I still plan to go to the gym but doing shorter and less intense workouts. That's my personal decision.

Now as far as your SIL goes - it's hard to say what is correct. Often m/c's are unforunately due to some problem with the baby although some medical conditions can predispose a person to having them. However I don't think I would want to cop too many knocks to the stomach or do something where there is a risk of serious falls. However you've heard froma number of women who played competitive sport, went skiing etc with no problems. A girl at work who is a snow skiing addict went skiing in the first trimester and is now 34+ weeks with a healthy baby.

I think that it is ultimately up to you what you choose to do and it's got nothing to do with what your SIL says. I agree with Michelle's post esp the last paragraph, Talk to your SIL about what you feel and make your own choices for your pregnancy.