Sunnyperch- So I haven't been modifying a lot of workouts but just this week we had a workout with a lot of box jumps. They started giving me heart palpitations (which I have been having a problem with recently...) so I went to step ups. I've definitely made changes to keep my intensity down. I don't wear a HR monitor and find that keeping the intensity down is the key. I am sure I am far over 140 though! It is tough - I want to push harder but I am trying to go with the "talk test" as my gauge. I feel like as long as I can talk, I have good oxygen flow going on!
My OB gave me a booklet that still had the 140 beats per minute guideline in it. I think that is pretty dated thinking. She and I discussed exercise and I told her I was doing Crossfit - I think she was vaguely familiar and she didn't seem concerned. She stressed to me the importance of only doing what feels right. I did a little research about the 140 limit because it does make me a little paranoid. I found out that the American College of Obstetricians and Gynecologists updated their position on exercise during pregnancy in 2002. I found this article which has lots of good info, but this paragraph definitely stood out as useful for us:
Given the variability in maternal heart rate responses to exercise, target heart rates cannot be used to monitor exercise intensity in pregnancy.
Ratings of perceived exertion have been found to be useful during pregnancy as an alternative to heart rate monitoring of exercise intensity.54 For moderate exercise, ratings of perceived exertion should be 12–14 (somewhat hard) on the 6–20 scale. Evidence of the efficacy of this approach is that, when exercise is self paced, most pregnant women will voluntarily reduce their exercise intensity as pregnancy progresses.55 Although an upper level of safe exercise intensity has not been established, women who were regular exercisers before pregnancy and who have uncomplicated, healthy pregnancies should be able to engage in high intensity exercise programmes, such as jogging and aerobics, with no adverse effects.
Here's a link to the whole article: http://bjsm.bmj.com/content/37/1/6.full
I hope this helps you like it helped me! I'd love to hear about your workouts and how things are going for you. I am definitely the only pregnant person at my gym but there is actually a woman on the Sept DDC that is a trainer!