An important part of being pregnant in Japan is registering with your local city/district office. When you do that, they give you a pile of paperwork, a mother-child handbook, and this wonderful little tag to place on your purse.
The Japanese says: Onaka ni akachan ga imasu
(In my stomach is a baby)
The paperwork and mother's notebook were the official reason I registered at the district office. This mark was my "real" reason.
Pregnant women display this mark on their purses to let others know their pregnant. In theory, other people are supposed to be extra helpful and considerate of them.
there are signs all around town giving special perks to women who bear the "ninshin ma-ku" (Pregnancy mark)
This is the most ubiquitous sign. It's found on all public transportation over the preferencial seating area. On subways, trains, and busses special seats must be left open for "the elderly, those with disabilities, those with infants, pregnant women, and those with health problems."
Since getting my pregnancy mark, I've been relieved to always have a seat on the subway or bus. Although, I always make sure to display my mark while I'm seated, so no one thinks I'm just a dumb foreigner who can't read the sign. (I have my suspicions some people think this anyways.)
The next sign is in front of the mall near our home. It reserves the handicapped parking spot for pregnant women as well as people with disabilities. Or maybe they consider pregnant women disabled, hard to say.
I've been told that the mark also allows you to cut in the line at the bathroom. I haven't had the nerve to try this out yet. But I'll let you know how it goes if I ever do.