This double sided Lucy Hugs Ricky keychain is straight from Season 2 Episode 15, "Lucy is Enceinte". In this episode, Lucy announces to Ricky that she is pregnant.
When Lucy and Ricky found out they were pregnant in the spring of 1952, they assumed that the I Love Lucy show would be canceled. However, the producer Oppenheimer brilliantly thought of writing the pregnancy into the script. After consulting with a priest, rabbi and minister, they went ahead with including a pregnant Lucille Ball in the script. They never did use the word "pregnant" in any of the episodes.