I have a friend, let's call her Rachel, who is friends with a very rich woman (over $100 million). Rachel is more of the first generation upper middle class. One time when Rachel went to Paris to stay at her friend's apartment, Rachel came back and told me that what she remembered most was a painting she had seen in a museum. Rachel said that the painting depicted a story about a woman who had been widowed and was poor. The widow was visited by a rich friend who was showing off her expensive jewelry. The widow had called for her children and showed them to the wealthy friend, saying "These are my jewels." I could understand why seeing that painting had meant a lot to Rachel during her visit with her wealthy friend at the Paris apartment.
I think the painting Rachel saw was a genre painting of Cornelia. This subject was very popular in the 18th and 19th century. Cornelia was a Roman noblewoman born almost 200 years before Christ. She was widowed and refused to remarry, devoting herself to raising her children. Cornelia is the origin of the "These are my jewels," quotation. I like theEncarta write-up on Cornelia, but I took this image from the Wikipedia article.
The idea of Cornelia and the rich woman has maintained its power over time, I think because our minds really do associate jewels with children. In Anglo-Saxon England, around 736 AD, Bede reports that the mother of the Abbess Hilda had a dream when she was pregnant that she pulled a most precious jewel from under her dress. This dream was understood to foretell the importance of the child in her womb. The metaphor of jewels for children even shows up in Freud's dream analysis. In Dora's first dream, she wants to save her jewelry box from a fire and Freud makes the association of the jewelry box with the woman's womb.