I was looking on the internet for answers about how safe it would be to work out while pregnant and here is a post that I found:
Expert: Helene Byrne - 2/20/2008
Question
I have a few questions I would like to ask you if that is ok? First, I recently read that it is not good to exercise vigorously for over 30 minutes while pregnant because it compromises blood flow to the fetus? I am currently very in shape and run for 45 minutes straight or will occassionally do a 90 minutes aerobic class, would you consider it ok to continue this during pregnancy? Also, this may not be true, but I heard that if you workout your entire pregnancy the weight will come off much easier after you give birth?
Answer
Thanks for asking these questions. There are so many myths and misinformation regarding prenatal fitness bouncing around the Internet these days, that it is hard to separate fact from fiction.
Athletic women like you can continue to workout at a more intense level than most women. Up until 20 weeks gestation, athletes can even perform intense interval training. The 30 minute "rule" is a minimum guideline, not a maximum. Make sure that on you heavy workout days that you take in more calories to compensate for what you've used up.
Continuing with your regular workouts will provide numerous health benefits to you and your developing baby. You'll grow a bigger placenta, have a stronger immune system, gain less weight, and bounce back much more quickly. You baby will have a stronger cardiovascular system from birth, and will even have a more developed cerebral cortex! Many now believe that fit mothers have smarter babies. The strength of your immune system will greatly benefit your baby via your breast milk. And yes, fit moms have shorter labors, especially first and second stage, and far fewer interventions and/or complications. So, you go girl!
Since the placenta stops growing at 20 weeks, its ability to transport oxygen is capped at that point, and women should slowly begin to taper down the intensity of their cardio workouts. You'll find that during the lasts trimester, when your baby is growing rapidly, that she will demand more oxygen and that your rate of perceived exertion will rise accordingly. After 20 weeks, stay in a heart rate zone of "somewhat difficult," don't pass your anaerobic threshold, or get out of breath.
Blood flow to the fetus in not compromised during aerobic exercise. This is a myth. It had been surmised that uterine blood flow might be reduced when exercising on the back, and that is why women are told not to exercise on their backs in the 2nd and 3rd trimester. But recent studies by the top experts in the field have now conclusive evidence that exercising on the back does not decrease uterine blood flow in a significant way. Dr. Clapp, who led the research, stated at a recent conference, that he believes that once ACOG, The American College of Obstetricians and Gynecologists, peer review his research, that they will no longer advise pregnant women to refrain from exercising on the backs.
