Courtesy or Special Treatment?

OK so I got into a heated discussion with my sister about this and I'm wondering what you guys think...

Everybody knows (or at least in USA) that when you are driving a car, you stay on the right side of the road. The same applies when walking on a sidewalk but thats just learned behavior...not legally enforced. So hypothetical situation... You are walking down the sidewalk and you see ahead that a obviously pregnant woman is walking in the opposite direction of you. In order to follow this "stay to the right" rule, the pregnant woman would be walking closest to the road when you pass each other.

My sister says it doesn't matter, that it is special treatment to walk on the left to keep the pregnant woman farthest from the road.

I say it is a courtesy thing, that keeping the pregnant woman away from the road is whats right to do. I would rather walk closer to the road than for her to have to do that just because she's carrying a child.

My sister says pregnancy is not a disability or an illness and that a pregnant woman is just as capable of watching for cars as anyone else. I do agree with that, but if a car were to swerve or anything I would feel guilty for a pregnant woman to be hit just because I decided to stay to the right.

What would you guys do in this situation? And would you expect the other person to walk closer to the road if roles were reversed making you the pregnant lady?