Dr James Clapp III, emeritus professor of reproductive biology at Case Western University in Ohio has been researching the effects of exercise in pregnancy for 20+ years. And, in the following article written for USA Today in 2007, you can read about women he has studied who stay extremely active during their pregnancies and still have wonderful, healthy babies and minimal complications.
For example, one woman ran a half-marathan at 7 months pregnancy and then ran another half marathon 6 weeks after delivery. (Six weeks! That's great!!) By staying this active, women reduce the amount of weight they gain (excess body fat weight that is, not weight of the baby), which means they have less to take off after baby is born and are less likely to retain this weight indefinitely afterwards.
When doctors push women to not exercise because they're pregnant, they really are pushing for more harm than good. Women who stay active during their pregnancies are more likely to encourage their children to be active with them, which leads to fewer obese and unhealthy children. They also are at a much lower risk for diabetes both during and after pregnancy.
I'm sharing this information with you all because recently I was doubting my intense activity regimin due to some negative comments by some on-lookers. With this information though, I'm going to continue being active and feeling great - I hope you all do the same (the pregnant ladies, that is).