I have have unusually dark colored bowel movements the last week. Is that a sign of pregnancy or something else? Almost like a dark chocolate color. (trying not to be graphic) But I wanted to know if this is normal or something worse.

Most likely something you have eaten

Have you been taking any iron supplements or eating anything that might have lots of iron in it as this happens when you get a lot of iron in your diet?

I have been taking pre-natal vitamins. Can that affect it?

Yes it most certainly can. This is normal to happen when getting lots of iron in your diet. I suggest you talk to your doctor about this. They will probably tell you the same thing but I don't want to get in any trouble by trying to diagnose anything. So bring it up to your doctor.

Just in case you are going to be a Mom, check out the following sites.
Also remember the golden rule - when in doubt, see your doctor. Just make certain that your stools don't get too hard, then you might need a medication to soften them a little.

Check out the following sites, they will help you through this a little more to reassure if you are.
http://www.mayoclinic.com/health/symptoms-of-pregnancy/PR00102 scroll down and even get answers on flying while pregnant, exercise, dangers, etc.
http://www.epigee.org/pregnancy/symptoms.html
www.askdramy.com (http://www.askdramy.com) The U.K. online doctor.you can post on a forum, or 'ask the Dr. Amy' with a click. The FAQ Tab on the homepage is also a good place to click and has a lot of good subject matter. P.S. Most of the articles are printable in PDF format.
Good luck, and keep us posted.

http://smileys.smileycentral.com/cat/15/15_9_16.gif (http://www.smileycentral.com/?partner=ZSzeb001_ZN)P.S. in the OB/GYN Clinic online, they have revealed a study that fish two to three times a week are very beneficial to you and the baby if you are expecting. Once I find the article again, I will post it for all to read.

Here's the PDF document with the results of the latest study on fish in diets for expectant mothers and the benefits. Hope this helps many of you.

http://smileys.smileycentral.com/cat/15/15_12_9.gif (http://www.smileycentral.com/?partner=ZSzeb001_ZN)