I would say it's not really safe and I'm sure your doctor would advise that you not do it. But I'm rough and i did it my whole pregnancy and I'm now 36 weeks and I've slowed down now. At 9 weeks your baby is still behind your pelvic bone so it is protected but you may want to take it easy just to be safe:)
I was always overly cautious! I definitely wouldn't play fight, just like when little kids do it... Accidents usually happen and you can't take it back once it happens