The Chinese in early 50's were going through a big baby boom period and the doctors were over-stretched.They devised a way of avoiding repeated visits by would be mothers. This is how the story goes:
A young chinese woman, three months pregnant went to see her local government obstetrician doctor who was very busy, his compunder saw her and asked her to quickly bare her tummy. He then reached into his desk and took out a rubber stamp, which he pressed below her navel and asked the young lady to go home.
At home, she and her curious husband tried to read the tiny chinese words printed on her belly, but they were too small. They then got a magnifying glass and tried to read the words; the stamp read: "When your husband can read this without the magnifying glasses, it's time to come to the hospital."