working out against dr advice?

Vicki
I'm going to be 10 weeks tomorrow. I've had one previous pregnancy that ended in miscarriage. My OB told me that I shouldn't lift heavier than 25 lbs. Before getting pregnant I lifted heavy (205 squat and deadlift when I'm 120). I was also told to keep my heart rate under 140. 
Has anyone else gone against their doctors suggestions? They seem a bit ridiculous. I'm also a Martial Arts and fitness instructor. My life is active and the restrictions don't make sense to me.