You sound like you are in good health which is very important, so you would be continuing your active lifestyle instead of drastically increasing your exercise level at this point of your life.

I would definitely discuss this with your medical health professional about this to determine an appropriate evaluation for you and your lifestyle. Miscarriages are also very common (about 25% of all women experience at least one but that statistic depends on which trimester and age group you are considering) and sometimes the cause is unknown. The body cannot sustain a pregnancy without adequate body fat and sometimes will reject the implanted fetus if severe abnormalities exist.

Good luck and let us know what your medical professional advises!