If the new parents don't know the baby's gender yet or prefer gender neutral baby things, you could make it gray with yellow polka dots or white with green polka dots. (littleredwindow.com)
Wearing a tie front yellow polka dot blouse — similar polka dot shirt here or here. (stylepantry.com)
She acted as if I had just marched up to the alter in a «Itsy Bitsy Teeny Weeny Yellow Polka Dot Bikini»! (redeeminggod.com)