There is a stigma attached to a woman during pregnancy.
The mystique is similar to a lioness protecting her cubs mixed with an emotionally unbalanced circus clown (the crying one). This alone scares men. Some buy shirts for the mothers-to-be:
These shirts and the like aren’t so much a WARNING to others as they are more of a reminder to themselves that “She is volatile.” Post-It notes were invented by a man. There is no shock there. We need to be reminded.