Because the OB/GYN's recommendations from the American College of Obstetricians and Gynecologists (ACOG) do not include any reference toward monitoring heart rate during pregnancy, for any reason, I feel that Active should support that stance. It is only cause for undue concern in a healthy pregnancy. There are many studies which have contradictory information and I feel it is important to stay in alignment with ACOG, who can disseminate these various studies for the factual information we all desire. Check out www.acog.org for more information...

ACOG's stance is that in a healthy pregnancy, heart rate is not a reliable indicator of intensity. They claim that RPE (Rating of Perceived Exertion) or Talk Tests should take place of HR monitoring and that pregnant women simply should not exercise to the "point of exhaustion". These guidelines are from ACOG's latest release in 2002

-Farel Hruska, Stroller Strides National Fitness Director, www.strollerstrides.com

I'm at 4.5 months, and have found my heart rate is not a predicable indicator. I use the breathlessness test - if I can't get my breath then I am going too fast. What this means for me is that during a run I will walk a mile first to get myself into the proper breath pattern before I start running.  Once you get a good blood flow going you should be fine.