I m 33 years old, 5 1, 112 lbs and pregnant with my 2nd. My first sonogram was this morning and the tech guessed I had just reached the 6 week mark. We saw the gestational sac , yolk sac, embryo and flicker of heartbeat but the tech said it was low at 50. Does this low heartrate definitely indicate an impending miscarriage and could it be linked to my workouts (I go to the gym 4xs/week but have decreased the intensity of my workouts).