Heart Rate During Pregnancy Exercise: What's Safe?

Question
Hi,
I have been working out for a year, step 3x/week for 1/2hr and lifting weights.  I am now 8 weeks pregnant and just got a heart monitor.  My heart rate was at 158 and I did not feel winded.  When I tried to bring it down to the recommended 140 I felt I wasn't doing much.  Is it OK to be at 158 for 15-25 mins. during the workout?  I do feel like I am fine during the higher heart rate, but I don't want to harm the baby.  Thank You

Answer
The American College of Obstetricians and Gynecologists, ACOG, dropped their recommendation that pregnant women limit their heart rates to 140 BPM in 2002. The 30 minute recommendation is a minimum, not a maximum.

Many very fit pregnant women, particularly those with a mesomorphic body type, can easily maintain a higher heart rate with out passing their anaerobic thresholds. As long as you do not feel out of breath, then you don't need to worry. Your baby will not be harmed.

In fact, studies show that babies "workout" along with their mothers, have bigger placentas, develop stronger cardiovascular systems, stronger immune systems, and even more developed brains than babies born to less fit women. So you totally rock!

You can maintain this exercise intensity up to 20 weeks along as this is when the placenta stops growing. From this point on, slowly taper down the intensity of your aerobic exercises. You'll also find that your rate of perceived exertion will rise as your baby gets bigger and demands more oxygen from you.

Since you are highly active, make sure that you stay well hydrated, and are taking in enough high quality fuel to support your increased metabolism.