Stigma

I have tried to post the same question before but haven't had much luck with anyone replying since it was an old thread and the question was pertaining to the first trimester. I am now in my 5th month and every doctor has told me that it's fine to exercise, that I can basically do whatever I want as long as I'm feeling OK while doing it, yet at the same time they did confirm that my heart rate shouldn't be over 140 bmp. This really confuses me as I'm used to working out at about 160-180 bmp and I find that it's too easy for me to reach 140 now, especially with the extra weight gain. That heart rate is just walking and when I was on the stairmaster the other day, it was 160.

Is this really a big no-no??? I'm so confused. I understand that overheating is not good but you have women doing marathon runs in their last trimesters and of course their heart rate is gonna be higher than 140. I don't find any benefit from walking and a real workout helps me immensely with stress, anxiety, depression, overeating, etc.

Please help! What are you doing for exercise? Has anyone done a fairly good cardio exercise program while pregnant and benefited? Other stories/opinions/inputs???

Thanks!