You really should check with your Midwife or Obstetrician. Usually, if you were accustomed to regular exercise before pregnancy, you can carry on within reason, but your heartrate should not rise above 140-145 beats per minute. Nor should to do any exercise which involves lying flat on your back, by the second Trimester.
I work in the Fitness Industry, but when I had my first ante natal appointment last week, the midwife banned me from even walking on a treadmill. Obviously I'm very disappointed, as I haven't done any exercise for 8 weeks, since finding out.
I have Fibroids and PCOS and she didn't think it would be safe to exercise, except for swimming, but I can't swim.