Well, I can understand a pregnant woman, how hard it is to seat vertically when you have about 5-6 month of pregnancy. Cause abdomen become very big, and from that moment it's hard to seat vertically.

And I have some great solution. As I know, the most comfortable position is half-lie position, like in car's chair. But it's very heavy for transportation. Well, my idea is to invent this chair from titanium material, because it's very durable material and very light, it would weight about 500 gr. And it is very transportable for pregnant woman.