How does the body adapt to pregnancy? What about Exercise?

Alright here is the blog entry you've all been waiting for! This whole time I've been talking about exercising while pregnant and telling you that it's good but isn't it time for me to start to prove it? I think so! Now this may take a few entries but I'm going to get started. The bulk of my information comes from a book called "Exercising Through Your Pregnancy" by James F. Clapp. Clapp has run many studies on pregnant women who continued weight bearing exercise throughout their pregnancies and compared them to women who did not. This book has a lot of great, detailed, scientific information and I would recommend it to anyone who is even remotely interested! 

Let's start by looking at the heart and circulatory system's adaptations to pregnancy. During pregnancy the circulatory system must change to support the mother's body but also that of the developing baby. When the fertilized egg implants in the uterus the outer rim of cells that will form the placenta release a hormone that causes a the woman's blood vessels to relax. This means that the elasticity and volume of the entire circulatory system (heart, arteries, veins) increases. This is what we refer to as "underfill" because now there is not enough blood in the circulation to fill it up, and thus blood pressure falls. This is the cause of a lot of early pregnancy symptoms such as feeling light headed, nausea, and fatigue. The body responds to this underfill by releasing hormones that cause the kidneys to retain more salt and water, thus the volume of plasma expands correcting the underfill problem. Finally blood volume, stroke volume, and cardiac output increases, which as I said before was necessary so that the mother's body can now support not just herself but also the developing baby. 
Now for the adaptations to exercise, quoting directly from Clapp's book, "Many classic studies... have clearly demonstrated that regular, vigorous exercise training increases blood volume, the size of the heart chambers, the volume of blood pumped with each beat, and the maximum cardiac output that can be achieved."  It also increases the bodies ability to dissipate heat, thereby helping to prevent overheating, and it also helps the body become more efficient at delivering oxygen and nutrients to tissues. Hmmm I'm seeing a pattern here, some of these adaptions to exercise are similar to the adaptations that a woman's body goes through when she becomes pregnant! "Therefore as you  might have already guessed, the changes produced by regular weight-bearing exercise actually complement those induced by pregnancy. Indeed the circulatory status of a normal pregnant woman at rest has many similarities with that of a trained nonpregnant woman during exercise." So, when a fit woman maintains her regular exercise routine during pregnancy, I be those cardiovascular adaptations to pregnancy are combined with their preexisting adaptations to training! That's the part that makes me the most excited! It makes me think that maybe if I keep up my exercise routine during pregnancy that I should be even stronger after I have the baby! Pregnancy could actually help me be a better athlete! That's exciting! I'm not planning on breaking my 5k record (23 min 45 sec) during my pregnancy but what about after! I'm not gonna lie, going running now is way more work than it ever has been, my heart rate stays real high even though I'm only running like an 11 minute/mile pace and some days I'm just totally out of breath and can't seem to find a rhythm. But I think this is normal simply because of how hard my body is having to work just to keep me alive. Even if I don't come back a stronger athlete than I was prior to being pregnant, exercising will still have been worth it because not only is it benefiting me but it's also good for my baby! I'll save that discussion for another blog entry!