Something that is extremely valuable, coveted, or held in high regard.
This is evidenced by the fact of gold is very rare, valuable, and pleasing to the eye. Also, a baby is treated as being just as valuable, rare, and with the creepy way and frequency that people (especially women) stare at them perhaps more valuable. The combined effects of these infers an exponential effect.
The race card is the golden baby of the politically correct movement.