Lucy and Ricky are crying as the episode comes to a close; the tears shed by Lucille Ball and Desi Arnaz were real.
Desi Arnaz accidentally flubbed the "Rock-a-bye Baby" song when Lucy confirmed being pregnant. They were originally going to do another take, but because Desi and Lucy's reactions were so natural they decided to leave it alone.
Lucy was five months pregnant at the time this episode was filmed.
CBS broadcast standards refused to allow the word "pregnant" to be uttered by any of the characters, so they said that Lucy was "expecting" instead. While this episode title uses "enceinte", the French word for "pregnant", the following episode (#2.11) uses the forbidden word in its title.