This article states that pregnant women who ride the tube can get a badge so people know they are pregnant and so they can get a seat. That's pretty neat!

"Middleton, the wife of Prince William, was gifted a "Baby on Board" badge by London Underground chief operating officer Howard Collins, according to the UK's Mirror. The badge is said to be worn by pregnant women riding the Tube to ensure they are given a seat, and to avoid any embarrassing gaffes should a non-pregnant woman be mistaken for needing a seat for that reason."

http://gma.yahoo.com/blogs/abc-blogs/tube-deprived-kate-middleton-gets-baby-board-badge-171706823--abc-news-celebrities.html

Can anyone see this happening in NYC or DC?