Chlorine pools are pretty toxic.
You know that horrible smell at the public pool? That "Chlorine Smell"?
That is actually the smell of other chemicals- when chlorine reacts with organic matter in a swimming pool, such as sweat or urine, a mixture of potentially harmful chemicals result, many of which are on the "Dirty Dozen" list of most harmful chemicals you can ingest.
So when you are at a pool that smells really strongly, it means that there is a lot of "Organic Matter" in the pool that is reacting with the chlorine. Pools that are cleaned regularly and have the correct amount of chlorine in them shouldn't smell as strongly as the pools that don't*Shudder*
There have been a number of studies done in Europe that are connecting child Asthma with breathing these chemicals in. When the chemicals are breathed in they create something called "Lung Proteins", the same thing that Cigarette smokers get in their lungs! The studies found that kids who swim regularly often have Lung Protein levels similar to that of a daily Cigarette smoker!
All of these risk are much greater at an indoor pool. The people sitting near a pool are breathing in almost the same amount of chemicals as the people in the pool. The more fans and ventilation at an indoor pool the better.
All that being said, I don't think going swimming a few times in a chlorine pool while you are pregnant is dangerous, but if you are planning on doing it on regular basis I would definitely research it. I personally am planning to use the Saline Pool at the gym as much as possible during my pregnancy, but I know that I will be taking DS to the public pool at least a few times this summer. But we are going to do outdoor pools only.
And of course shower afterwards...you just got out of a community bath!!