You're fine for a little while. I remember there was a furore over Adine Wilson playing in the 2007 netball world cup final before telling her team she was pregnant and all sorts of doctors came out of the woodwork to discuss when it was and wasn't safe, I wasn't that far along behind her so found it most useful!
Anyway the general consensus was that before about 14 weeks the baby is still down in your pelvis so protected from any knocks. When you get a midwife ask her though - I was measuring 2 weeks ahead with baby popping out higher than he was supposed to be, so she *strongly suggested* that I stop playing hockey at 12 weeks, a couple of weeks sooner than I'd intended to (which happened to be before we'd told people so that made it tricky!).
I was interested to find out that in the early stages of pregnancy you're actually likely to be at your fittest, because your heart has already started enlarging to pump around all that extra blood, so it's very efficient, but you're not yet carrying around the extra weight to slow you down

It's times like that I thought pregnancy was cool. Course hyperemesis kicked in a week later!
The other thing to take into account is that during pregnancy all your ligaments loosen so you can be more vulnerable to sprain type injuries. So the danger is more to you rather than the baby. I was willing to risk it but plenty aren't
Congratulations, and hope that helps!